#httyd oswald the agreeable

[noctusfury]

Do Dagur and Heather Have Anglo-Saxon Ancestry? (HTTYD/RTTE Theory)

Hello, my fellow Furians! Here's another HTTYD article for you today!

In this article, we'll ask the question of why Heather doesn't look like the other Vikings and why her name isn't a Viking or Barbaric-Archipelago-ian like the others. 

Here is my take on this.

(This is also major thanks to @valiantwarrior37 for helping me out concerning this and we had a lot of fun discussing this several years ago.)

My Theory and Headcanon:

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Their Physical Appearance:

Here's MY theory and headcanon for this question:

Heather — and possibly Dagur — have Anglo-Saxon blood!

If this is the first time you've heard of this, or if this sounds a bit "out there," then please hear me out!

Now, you're probably wondering, "Noctus, why do you think that Heather — and possibly Dagur — have Anglo-Saxon blood? They're BERSERKERS!" 

AH! Well, I didn't say that they were FULL-BLOODED Anglo-Saxons, now, did I?

What I mean is that they're half Anglo-Saxon and half Viking. The Viking half from their father, and the Anglo-Saxon half from their mother. Or even a quarter Anglo-Saxon from their father's side (or mother's side), maybe?

Now, why do I think that?

Because we literally know nothing about their mother and very little about Osvald the Agreeable. We don't know what they looked like, how they met before Dagur and Heather were born, or if maybe the mom died and Osvald remarried—WE. KNOW. NOTHING!

Yes, Heather looks nothing like a Viking; that we can agree with. Neither does her name. My headcanon is that she takes it after their mother, or even grandmother, who's quite possibly Anglo-Saxon by blood. The reason why is probably the hair-color and Heather's physical appearance. It's very common in Anglo-Saxon women. Anglo-Saxons were well-known to have a lot of brunettes (though they did have blondes, too). Black-haired people as well. Even a few redheads, but those weren't as common as the Celtic and even Nordic peoples.

We must, of course, consider, that Dagur and Heather could be half-siblings, meaning that they could've had different mothers.

Now, we don't know what she looked like, nor what Osvald looked like. Osvald could've had red hair and green eyes, while the mother had black hair (or dark brown hair) and whatever-colored eyes she had (let's say, blue, for argument's sake). So Dagur looks like Osvald and Heather looks like the mother. Or Osvald could've had different eyes while the mother had the green eyes, so both kids have their mother's eyes, but Heather also has her mother's looks and hair. 

If Osvald had black/dark brown hair and green eyes (which I doubt because Vikings don't really have that combination usually) and the mother had red hair and blue eyes, then Heather would have the form of her mother yet the hair and eyes of her father, and Dagur would have the form and eyes of his father, but the hair of his mother. 

If Osvald had black/brown hair hair and blue (or brown) eyes, and the mother had red hair and green eyes, then Dagur would've had his mother's hair and eyes and the build and personality of his father while Heather had the form and eyes of her mother and the hair of her father. Actually, the OC that I made to be Dagur and Heather's mother has this combo (though, I'm not sure if I'm going to be keeping that look).

The problem with this though is that I doubt that Osvald has black/dark brown hair and whatever-colored-eyes-that-aren't-green because look at this:

And this:

These are concept artwork of Osvald the Agreeable. The problem though is that none of these look like Osvald in the Race to the Edge series in this shot:

Look at this guy! Oswald in RTTE looks taller and, while buff-looking, isn't a rounded square block. To be fair, though, RTTE is a product of Netflix, not Cartoon Network, so it make sense that the designs for Osvald would be different.

Also, I really wouldn't be surprised if he has red hair and green eyes. Or red hair and blue eyes.

If any of you are experts in genetics, please clear this up for me. 

Please?

Anyway, comment on these two questions:

1) What do you think Oswald looks like?

2) What do you think Oswald's wife looks like?

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Heather's Name:

Okay, back to Heather and Dagur — but mostly Heather.

Another possible proof to my headcanon as to why Heather may be half (or quarter) Anglo-Saxon is. . . well, her name. Heather is a Middle-English name used between the 1100s-1400s — though that's most likely its peak period. It wouldn't be surprising if it was used as early as the Anglo-Saxon period. It was used by the Anglo-Saxons (particularly the Northumbrians), the Anglo-Normans, and the Scottish later in the medieval period. So if her mother gave her daughter the name Heather, then she, or Heather's grandmother, would probably most likely be Anglo-Saxon, as Heather is an Anglo-Saxon name, more or less. Keep in mind that Heather is merely an Anglicized version of the name. Her mother, if she was Anglo-Saxon, would've said the name in her Anglo-Saxon language, but when she named her, her mother would've used the Norse language, so it could easily be Lynga or Lyngja or Lynghild or Lyngrid — Lyng meaning "heather" in Old Norse; another possibility is Erika, which can translate into "heather" in some languages. Quite possibly Middle-English as well.

Another possibility — but less likely — is that Heather might've inherited the name from her mother or her grandmother (depending on who was full-blooded Anglo-Saxon). It may have been that her grandmother was the Anglo-Saxon and not her mother. Honestly, we don't know. Dagur says himself that Heather and he are the only family each other's got, which means that everyone in the Berserk family has . . . retired! We know almost nothing of their family and we don't know what any of them look like.

Heck, Dagur and Heather could've been half-siblings for all we know — Oswald's first wife having Dagur and the Anglo-Saxon gal having Heather. We simply don't know.

Ugh! The possibilities are ENDLESS!!!

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Conclusion:

So regardless whether Dagur and Heather's mother was red-haired and green-eyed, or red-haired and blue-eyed, or black-haired and green-eyed, or black-haired and blue-eyed, or whatever hair/eye combo you want to give her, it can literally be any of these combos because we don't know what Oswald and his wife look like. If she has red hair and blue or green eyes, she may be Scottish or Irish (or maybe one of those few Anglo-Saxon ladies that's a red-head). Or she may be Anglo-Saxon. Or she may just be 100% Norse and Heather is simply an Anglicized version of her Viking name that means "heather". After all, Hiksti means "hiccup" in Icelandic, which is the closest form of Old Norse that we can sadly get.

If anyone can correct me on this, please let me know. I'd be interested to know if there's an Old Norse word for "hiccup". 

Anyway, I hope you guys enjoyed this article. Thank you for your time.

So, in conclusion, my theory and headcanon is that Heather and Dagur's mother is Anglo-Saxon and that they're half-bloods -- which can explain her appearance and name. It doesn't go against the canon, but it also can't be confirmed either. Though you can't confirm anything concerning Heather, Dagur, and their family because their family is practically "retired" in Valhalla having a grand ole time partying and feasting and fighting people every day for eternity. lol XD

Regardless if she's half Anglo-Saxon, half Irish, half Scottish, or just 100% Norse with an Anglicized version of what would've been her Nordic name, this is just my nest egg on the matter. I hope you enjoyed it.

So please tell me your thoughts, my fellow Furians! Who do you think Heather is? Do you agree with my headcanon that she's part Anglo-Saxon? Or do you think that she's Irish? Scottish? Or just 100% Norse?

Also, what do you think their parents looked like, and what did Dagur and Heather inherit genetically from them? Or do you think that Dagur and Heather are half-siblings?

I can't wait to hear your thoughts!

Thank you so much for reading! I hope you've enjoyed picking apart this question as much as I have. 

Farewell and happy flying to you all, my fellow Furians!

Long Live the Night!

— Noctus Fury

[krikunjayvoice]

I'm sure they knew each other.

[sk-yay-sk]

[sarnai4]

Went Out For Some Milk

I think that Dagur and Hiccup have more in common than most people realize. An underrated example of this is how they both have parents who just plain abandoned them. To a certain extent, I understand Valka and Oswald. On a deeper level, I really can't get it at all. Here's why:

I get that Valka didn't willingly leave. She was taken by Cloudjumper. That's not her fault in the slightest. She was trying to protect her baby and was taken by a spooked dragon; however, why did she stay gone? She learned how to fly on dragons. Therefore, she had the means to return. The idea of her not being able to come back is gone. The realm with the dragons wasn't too far from Berk. She could ride a flying creature. The next suggestion is that it would've been unsafe. That's the one she used to explain it...but how? I'm genuinely curious if anyone has a reason because I can't think of it for the life of me. Just have Cloudjumper drop you off near Berk, swim to shore, and say you escaped. Or don't say that and try to gradually get the other Berkians to accept dragons. Heck, if she loved dragons so much and didn't want to ever be away, she could have flown to Berk and been like, "Hey, hubby, I'm a dragon rider now. Be cool with that and we can stay together." Stoick probably would've loved her enough to accept one of these. He loved her enough to accept that she made him a single dad for 20 years and wasn't even upset. It's also not fair to Hiccup that he grew up without a mom because she was too scared to be herself around the Berkians or risk losing her new freedom away from the island.

Oswald runs into the reverse of this. For him, I understand why he didn't return. The guy was shipwrecked on an island with dragons who didn't want anyone leaving. My issue with him is that he left in the first place. Why did he go? Why did he not tell anyone? Dagur never should've been able to convince the other Berserkers that he killed Oswald because the man should have told the others he was heading out. If he was going to a peace treaty signing, I'm sure he would've gone with more people. As a chief, it's irresponsible to not let his Vikings know where he'll be going or if he will since they might need his help. As a father, it's irresponsible to leave his son 50,000+ people to be in charge of without so much as a goodbye first. All he had to do was tell someone. An argument could be made that he told Dagur, but the question then becomes why on Earth would he do that and not tell anyone else? Mini Dagur isn't the person you give your location to so that he can be your emergency contact. If he even paid attention, he'd probably laugh at the idea of there being an emergency. Even still, I doubt that Oswald told him because Dagur seemed to really have no idea where he had gone. So, it's highly likely that Oswald just decided he had enough of being a chief and dad, then went to the great beyond.

I'm sure these are both unpopular opinions, but these parents really do bug me. What annoys me more is that I don't think either is shown to be anything other than loving despite that. It's unfair to their kids. I don't want the movie to tell me Valka is just the best mom ever and that they're going to be a happy family now that they found her. She could have returned to them years ago and we wouldn't have had that sad episode back when they were kids with poor Hiccup being desperate to find the one item his mom had given him since that was the only thing he had to remind him of her. I don't want to see a happy scene with Dagur reading about how much his dad loved him. Oswald should have proven it by not abandoning him, then in that same episode with the supposed happy moment, Dagur wouldn't have voiced his doubt that his dad did in fact love him. Just a little something that irks me, but I'm curious what everyone else thinks.

[ask-viggo-and-dagur]

hey viggo can you tell us about your parents then dagur too🫤?

Dagur: Well, Viggo already talked about his parents a bit here. I don't think he wants to go into more detail.

And, well, I never really knew my mother. Fatalities during childbirth were very real back in my time, and she passed while birthing Heather. Which... I blamed Heather for taking her away, but that's another story.

My father... Oh, my father... i wish I'd appreciated him more. I wish I'd listened to him. He was a noble man. He was brave for wanting to make peace with others rather than war. War is easy. Peace? Not so much. I respect him now in his death, but I wish I could have respected him in life too.

[chaoticskyy]

Since we know thar Drago killed the whole bunch of chiefs and only Stoick survived. Do we think that Oswald the Agreeable was just absent or that he was next in line for the chiefdom of the Berserkers and then started his raids as Oswald the Antagonistic?

[galaxyregent]

Here we have Dagur's Family, his mother Iona and his sister Brenna as a child. As you can see Brenna and Dagur favor their mother. I imagine Oswald had red hair too, though faded from the years. All three of Oswald's children got his eyes. Heather got dark hair from her mother.

Iona was a fierce and well respected warrior of the tribe, coming for a prominent family. She came from a family where she had one brother (Harold/Herald) and two sisters.

When I picture Iona and Oswald's relationship, I dont picture one of deep love but practicality. Iona was a good match for the chief and she found fulfillment in bettering her tribe and assisting him in war. She was never the type to stand still. Even though they weren't in love, they respected each other deeply. There was never a whisper of infidelity on either party while Iona lived.

Iona loved her children fiercely, wanting only the best for them in the future. It was actually more from Iona than Oswald the children get their mental instability from. Iona was great at managing it, on the battlefield she always let loose. For those who don't know, Berserkers were a supposedly real type of warrior among vikings. They would drink some kind of medicine, likely a serious stimulant, and charge into the battle fields, destroying all in their wake. It was said in battle they couldn't even differentiate between friends and foes so even allies had to give them a wide berth.

Brenna and Dagur loved their mother in turn, but only Brenna remembers her with any clarity. Still, Dagur remembers the fierce-some warrior his mother was from stories and faint memories. In BB I always right Dagur having deep respect for women, which seems to be canon too. That was partly due to Brenna being a domineering presence when they were children. She forced him to do her chores a lot.

It's never been clear why Oswald became agreeable, but I have a theory in the BB universe. Brenna is older than Dagur, and when she was born, there were many talks about a potential spouse. Wars between the tribes make intermarriage difficult, so they were trying to think of a spouse on island. However it was difficult, the population of the Berserker tribe is pretty much all related, more or less, especially the more influential clans. Now, inbreeding was nowhere near as understood as it now, but people understand cause and effect. Blood being too close has long since a valid reason to dissolving marriages of aristocracy.

When tribes are at war, blood becomes concentrated leading to sickly babes and deformities. Oswald found that every potential, suitable partner for Brenna was too close in blood. Then he had an idea. Even though he was at war with other tribes, he respected their leaders as warriors and men. What if there was a way to conquer tribes without bloodshed? What about marriage?

Slowly he begins his journey and establishing peace with other tribes. Brenna is promised to young heir of Hysteria tribes, one of his chief rivals. This bring peace and boost of commerce and fresh blood into both tribes, alliance also helps with dragon problem.

Peace with the Hooligan tribe is equally important, so he's thrilled when Stoick has a daughter while he has a son. Considering the difficulties with Hiccup's birth and the slew of failed pregnancies prior to her it's unlikely Stoick would have another child. This is confirmed when Valka is taken and Stoick refuses to take another wife.

It's an added bonus because law would support Hiccup's right to inherit the chief mantle. In the beginning it looked difficult because Stoick wanted his girl to stay close and resolve the succession crisis by marrying her to his nephew, his next closest relation. Eventually, Oswald convinces him to marry Hiccup to Dagur.

This plan actually kind of works because four of his six grandchildren are chiefs in their own right; his three grandsons through Dagur and his granddaughter Silvi through Brenna. Each chief ruling over a powerful tribe.

Iona means both Dove and Island

Brenna means burning or torch, again referencing her hair

[detdeldragons]

Chapters: 12/? Fandom: How to Train Your Dragon (Movies) Rating: General Audiences Warnings: No Archive Warnings Apply

Excerpt from the chapter “Dear Oswald.” Heather and Windshear find some shelter to get out of a storm, and Heather passes the time by reading a letter from a mysterious author.

“With each passing day I feel less in control of my own brain, more unhinged, more...deranged. There is a venom inside of me that wants to poison the world around me and deprive them of what I've been forced to live without. It is wrong, and I know its wrong, but I am the Chief and I need to be strong and how can you be strong without showing the world what you are willing to do in your own name? When dragons burn our homes and blizzards decimate our crops and other Vikings raid our shores what else is a leader to do other than be strong? And there is no one I can tell, no one I can speak my fears to, for if I speak my fears then someone might hear and use them against me and tear away the only thing of yours that I still possess - your chiefdom.”

This series of short stories features the various Vikings living in the Barbaric Archipelago. I have stories about Hiccup, Astrid, Heather, Fishlegs, Snotlout, the Twins, Stoick, Johann, and more. Hope you enjoy!

[misterrttegrimborn]

Eminem - Without Me

(my edit)

[headfullof-ideas]

Presenting two more characters and their redesigns in my HTTYD/The Deep story! One is more involved in the story, but the other makes PLOT, and neither really ever interact or connect to one another plot wise to my immediate knowledge in the overall story.

Introducing Savage and Eret!

Savage is not an Outcast and Alvins right hand man, but a true Berserker warrior, serving Oswald and his family for years. But when Oswald the Antagonistic becomes Oswald the Agreeable, Savage starts to grow restless. The Berserkers aren’t at war with the Berkians and surrounding tribes anymore, Oswald trying to maintain a semblance of peace in the dragon-war ridden Archipelago. Savage is a follower, not a natural born leader, but years of peace treaty after peace treaty, and babysitting Oswalds whelps has made him seek out other like-minded Berserkers, planning an uprising against the passive Chieftain. Oswald seemed to have caught on to what Savage was doing, escaping their attempted assassination, and now Savage is trying to commandeer the Berserker Tribe as a whole through sewing doubt amongst the tribe against Oswalds children, and trying to pit the siblings against one another in hopes they’ll simply get rid of the other for him. Savage isn’t good at thinking things through though, especially what the aftermath of his plans to stage a coup or civil war amongst the tribe to try and take leadership might be.

Eret son of Eret is a budding Dragon Trapper, partaking in his father’s business of trapping dragons and bringing them to Auction Markets run by the Grimborn brothers. Dragon Trapping was introduced to Erets family through his paternal Grandfather, with loans being taken from the wrong people, with no money to pay them back leading his Grandfather to Dragon Trapping. With similar habits being passed on to his son, Eret Sr, Eret has been taken on as crew for his fathers quest to pay off the debts his grandfather failed to pay, and his fathers own drunken mistakes. Eret isn’t sure how to feel about it all, his father pushing the looming mantle of Captain on to Eret as his eventual future, leaving whatever debts his father fails to pay before retirement for Eret to try and absolve, with old bedtime stories from his deceased mother and her side of the family speaking of dragons being more than wild animals. Eret’s been grappling with his internal struggles for a few years now, and a sudden interaction with some Archipelagon teenagers apparently riding dragons only rattles his inner beliefs even more.

I decided to go a bit of a different route with Savage in this story, making him a member of the Berserker tribe instead of the Outcasts. There are a lot of elements of his prior design still in this one, but he’s got a lead part in a lot of the early Berserker central arks and plots, especially in Heathers early story, and why she makes some of the decisions she does in Riders and Defenders of Berk, which has a sort of butterfly effect on the way she is in RTTE. He’s not a MAIN villain like the Grimborn brothers, Alvin, Heather, Drago, and a certain someone from the games, more of a small villain and a reoccurring nuisance. He gets his comeuppance however, as he’s not good at thinking things through, especially in the long run, and eventually gets revealed for all his nefarious schemes, and promptly exiled

Eret is a little different to the swashbuckling Dragon Trapper that’s in HTTYD 2, but he’s also nearly five years younger, a little older than Dagur and around the age that the riders were in RTTE. So, eighteen-nineteen-nearly twenty. He’s not Captain of the ship yet, and dealing with a lot of inner family struggles and trying to come to terms with what his future may hold. Generational and pawned off debt is how I play off (Headcanon wise) how he came to be under Drago’s employment in the films, and I’m playing with the setting of the early stages of how that happened here. With his grandfather and father both taking loans they couldn’t keep or pay back, and turning to Dragon Trapping to try and pay them off. Afterall, dragon parts and living dragons sell for a LOT of money. The Dragon Riders throw a bit of a wrench in things though, and Eret ends up being one of their first allies beyond Dagur and someone else in the Archipelago. He’s also a little shorter and not nearly as beefy as he is five years from then, not having the experience to build up that kind of muscle yet. I did this partly because of his age, and partly because Nico Marlets early concept art for him (whose HTTYD art I love and want tattooed to my brain) had him being a little more scrawny, and so I thought that was a nice callback

More characters to come…eventually, as it takes time to draw these, especially with the designing process I go through

[violet-moonstone]

Thinking of that one scene in shameless where mickey comes out in front of his dad and they get into a fight and after they get separated mickeys all bloody, pinned up against a car by a cop and still screaming at his dad (who's told him to get out of his house)

"Fuck you, dont worry about it! Ive been staying at ian's since youve been in the can, bitch! Guess what weve been doing daddy? We've been fucking!" (Humps car violently) "and i take it! He gives it to me good and hard and i fucking like it!" (Spits out blood) "I suck his dick and i fucking love it! Fuck you!"

I LOVE THAT SCENE

And i think it would be great inspiration for an eretlout fic or a dagcup modern au in which oswald is still alive but not so agreeable

Im very much considering doing something similar to this in my httyd 3 rewrite (between snotlout and spitelout)

[noctusfury]

Osvald the Agreeable by Noctus Fury

Hello, everyone! Today, here's another HTTYD edit for you. This time, it's Chief Osvald. I used one of the art concepts of him from the show for it, though we don't know his EXACT appearance, sadly.

I also kept the guards and the banners, since they're pretty cool. And it just looks like a Chief has entered the room! 😎

This is a scenario where Osvald never left, nor did he die, but continued ruling the Berserker Tribe, and came on the ROB episode "Twinsanity", hence maybe, plausibly, preventing the Berserker War from occurring. But who knows, since Dagur is Dagur. ����‍♂️

Other fanworks in this series are here, here, and here.

Thank you for your support and I hope you have a wonderful weekend!

Long Live the Night!

— Noctus Fury

[krikunjayvoice]

Another kid in the chat finished watching the series and we remembered, that I had a fucking theory and it fits the lore of the universe very well. And it concerns two of the most mysterious characters that we were not shown — Oswald the Agreeable (Dagur and Heather's father) and Viggo's grandfather (whom we named Ulric, and took the nickname from the book). I called it the Dragon Eye Saga and I would like to see a spinoff about this couple. The grandfather's fate is unknown, but I remember the moment with the discovery of the Dragon Eye. It was the Grimborn ship where in the captain's cabin there was a skeleton of a large man clutching the device. And also Viggo's words that the DE had been in their family for centuries (so he saw it, trivially in childhood or youth, and he knows how it works.) But why was it lost and he was looking for it? And Oswald hid the most important lenses for the DE in his family. That's why it seems like there's a connection between the two. The theory is that the two of them were able to decipher the lenses of the device, and perhaps they were not just allies, but friends.

And apparently they both understood the danger of this thing in the wrong hands. Which is why they decided to hide it, and the lenses. Some lenses were hidden in the Grimborns style — with traps and riddles, others in unusual places. The lenses were hidden, Oswald decided to keep one for himself, and give the other two to his children. Ulric kept the device itself with him. Apparently, towards the end of his life, he went on a voyage, leaving Viggo as his successor. But he did not return. The Reaper ran aground and Ulric died there, holding the Dragon Eye even after his death.

Oswald went to hide the most important lens, which belonged to him, and eventually suffered a shipwreck, after which he got stuck on Vanaheim and ended his life there far from his beloved children.

Perhaps a compelling reason to urgently hide DE and the lenses was the appearance of Drago Bludvist and his idea of an army of dragons. After all, an army needs a dragon king, and DE leads to him.

[sarnai4]

Misunderstanding

This honestly isn't even so much of a headcanon as it is a small idea I might use one day in a fic. What if Oswald had histrionic personality disorder and Dagur has general personality disorder (he probably also has several other disorders, but let's focus on this one)? This could have caused so many issues in communication for them. Oswald is extra dramatic and loves being the center of attention, all the more helped by his agreeable image. Turns out that it's not just his journal which is hard to understand. He regularly speaks in the most impressionistic way possible. Claude Monet would be jealous of his impressionism. And then we have Dagur who naturally draws attention, so it's already putting him at odds with his dad who wants that for himself. With GPD, it would make his perception of people, events, etc. really affected. So, Oswald speaking vaguely isn't just frustrating, it's darn near impossible for him to know what his dad means. He's also got this version of himself that he perceives as really reasonable despite what everyone else says, so when Oswald gets annoyed, it just makes no sense to him. More and more, the two grow apart until the day Oswald can't take it anymore and leaves. No one even thinks twice about this, assuming the hothead must have been the one to kill him. Dagur finally interprets something correctly - that the other Berserkers fear him. It's between embracing that and risking them thinking he's just some weirdo. He goes for the former and doesn't look back for years.

[dragonnnfly]

There might be some people that don’t know this.

But this is what Oswald looks like.

And I enjoy using facts like these to get a picture of the missing parent. Aka, Dagur’s and Heather’s mom was the red-head.

[farads]

Something that's been bothering me for a while is the Heather - Oswald disappearance timeline and how little it makes sense based on what characters have said and what was written in Oswald's letter to Dagur. But I think I've come up with something that kinda works?

For the timeline we have:

ROB episode: Twinsanity - the treaty signing with the Berserkers is annual, Stoick etc were confused that Dagur was now chief meaning that the most recently they've seen Oswald was one year before the events of ROB

this means that Heather is 13/14 when he goes missing as is the rest of the gang.

HOWEVER it is stated that Heather was set adrift as a child and early enough that she has almost no recollection of her life in the Berserker tribe. Her memories also show the hands of a child who is - at most - eight years old and very likely younger than that.

This leaves a >7 year gap between when Heather was set adrift and when Oswald disappeared.

If this had been addressed in searching for Oswald and chicken it would've worked out fine but in Oswald's letter to Dagur he mentions he hopes Dagur takes good care of her.

At this point heather has been missing for 7+ years and Oswald should know that so why does he imply otherwise? Especially with no mention of her going missing?

The only way I can think of this working logically is if Oswald had some kind of memory loss. There are several possibilities (early onset dementia, various forms of trauma induced amnesia, etc) personally I think dementia fits the best for reasons I'll explain below.

if we look at the cave drawings he does of Dagur and Heather, they both look really young. Especially for heather it's clear it's how they looked several years prior to ROB. Which would make sense, if he's forgotten some or all of the past few years, he would remember his kids looking younger (especially Dagur) and he wouldn't know Heather has been set adrift (especially if she was older (5-6) when she went missing) or that Dagur very clearly hasn't taken care of her.

Memory loss may also explain why his journal was so disjointed and hard to follow.

Afaik some memory loss conditions like dementia (especially the beginning stages) have both moments of lucidity (when he could write the letters but still 'living in the past' ie before Heather was lost) and confusion/ideas that no-one else can understand (when the nonsense/dangerous journal entries were written) it's also very likely that at some point he DID have specific questions he wanted to answer that eventually got clouded mentally and made his work incomprehensible.

As for how his journal somehow made its way into Dagur and Heather's hands instead of being shipwrecked with him. He may have seen the island from a distance and drawn the Bewilderbeast skull and then returned home (maybe was running late to something - like a treaty signing - and couldn't stop) and left his journal with the Berserkers, then at some time later, decided to go and explore the island without telling anyone (dementia patients are known to wander off) and shipwrecked. He very well could've tried to leave and the Sentinels stopped him (wrecked his ship) because he hadn't proven himself yet. Only then did he decide to make the most of it and help the sentinels fight off the grim gnashers.

As for his death there are plenty of possibilities because living isolated means that even is something minor goes wrong it can kill you. Disease, old age or injury could have caused it and even if they were usually minor, because nobody was able to care for him, whatever it was became fatal.