#the demons that provided tharizdun with the power to create the abyss are called obyriths if you're wondering btw

[swordscleric]

I don't know if anyone's gone through the original Dawn War pantheon* and compared the events of the Dawn War to the events of the Calamity, but it's interesting comparing how Tharizdun acts in the Dawn War to how little we know about it as the Chained Oblivion and might be useful as a theory-crafting aid for how the Chained Oblivion fits with Predathos**.

In the Dawn War, Tharizdun was a normal god, driven mad by extradimensional demons who provided him with huge amounts of power and attempted to force him to open a portal in the Astral Plane to release them. He took this power, and instead of releasing them created the Abyss. He and his would-be masters fought to a stalemate over control of the Abyss, until the rest of the pantheon found out and sealed him away, leaving him chained to a remote part of the Abyss[1].

By contrast, the Chained Oblivion is "something other entirely"[2], "less like a god and more like another world"[3]; it's been categorised as not of the Primes or Betrayers[4], and generally Matt has leaned much more into the cosmic horror vibes (sans a connection to the Far Realm) of the Chained Oblivion. It's a creature of "roiling ink and hungry darkness"[5], and was sealed at the bottom of the Abyss by the Dawnfather and the Knowing Mistress, with support from the Allhammer and the Changebringer[2, 3, 6]. The Chained Oblivion also wants to consume all and end the world and is kept at arms length by the Betrayers[5], and as a result of that plus its association with an unknowable hunger some people have now associated it with Predathos or think it and Predathos are of a similar species.

I think the Chained Oblivion is not Predathos in another form, but I do think that it's of a similar species. Looking at the Dawn War, and assuming (with the full acknowledgement that I'll more than likely be wrong) that Matt will stick as closely to the Dawn War as he has in the past, I think the Chained Oblivion is a smaller and weaker being of nothingness that decided to forge its own path instead of following Predathos' lead. My gut instinct is that the Chained Oblivion, seeing Ethedok and Vordo get eaten, took up Ethedok's mantle of darkness[7]*** and avoided working with Predathos and porentially fought the God Eater in order to survive and work its own odd plans of destruction. The Chained Oblivion makes a lot of plans to try and free itself (see the Angel of Irons or Cognouza), so I wouldn't be surprised if its propensity towards planning was present from the very moment it set foot on Exandria. Does this mean the Chained Oblivion will be let loose to fight the God Eater if Predathos is released? I doubt it, considering that it nearly killed the Knowing Mistress. And we know how the gods feel about family.

Footnotes

*The Dawn War pantheon is the slimmed down pantheon used for 4th edition D&D; can be found on page 11 of the 5th edition Dungeon Master's Guide. Used by Matt for the Primes & Betrayers with the addition of Sarenrae from Pathfinder.

**I'm aware of the pitfalls of using existing narratives and non-Exandrian lore to try and predict what's going on in CR at this moment in time; while there's not a 1:1 overlap between other D&D worlds' lore and Exandria, some of the major relationships do stay the same. For example, Pelor, Ioun and Tharizdun are all linked in Exandria and in D&D "canon" (Pelor, Ioun and Tharizdun all looked into the Far Realm and saw mysterious secrets, secrets which drove Tharizdun to want to destroy the universe as per Gates of Madness (2010). Additionally, Tharizdun is deeply associated with the Abyss across both settings). Bear with me.

***Zehir, the Cloaked Serpent is also associated with darkness; however while the Lawbearer and the Platinum Dragon are associated with order there is no explicit god of order which was Vordo's other domain. The Chained Oblivion is explicitly described as a god of darkness in both the Explorer's Guide to Wildemount (page 27) and the Tal'Dorei Campaign Setting Reborn (page 34).

References

1. Demonomicon (2010), pages 7-9. The wording of how the sealing took place is intentionally vague as it's a plot hook for DMs to expand on in their campaigns.

2. Titles and Tattoos, CR Campaign 2, Episode 84, from 14:00.

3. Explorer's Guide to Wildemount (2020), page 27.

4. Matt's Discord post during Nick Marini's AMA (linked here).

5. Tal'Dorei Campaign Setting Reborn, page 36.

6. The Endless Atheneum, CR Campaign 1, Episode 106, from 1:08:16.

7. Axiom Shaken, CR Campaign 3, Episode 43, at 3:02:19.