#ik it's a common interpretation that he thinks his mother chose to die too (understandably given jkr's intent)

[slitheringghost]

Slytherin Locket Cave: The Life And Death Of Merope Gaunt

I wanted to explore one of the most interesting details of Voldemort’s characterization: the extensive protections around the Slytherin locket horcrux, which exist as a step-by-step re-enactment of Merope's suffering - referencing his mother's actual death, but perhaps more prominently, her state of drowning in despair in the Gaunt home due to her family.

The Locket's Significance

Tom Riddle initially hears of it from his uncle:

“Ar, he left her, and serve her right, marrying filth!” said Morfin, spitting on the floor again. “Robbed us, mind, before she ran off! Where’s the locket, eh, where’s Slytherin’s locket?” Voldemort did not answer. Morfin was working himself into a rage again; he brandished his knife and shouted, “Dishonored us, she did, that little slut! And who’re you, coming here and asking questions about all that? It’s over, innit.... It’s over....” He looked away, staggering slightly, and Voldemort moved forward.

Making his uncle look at him to Legilimize him, Tom views the Bob Ogden memory - and later wipes his uncle memories till that point. (I assume LV got all the same Merope details and memories that Dumbledore shows Harry in HBP, and likely even more.)

We first see Slytherin's locket when Marvolo strangles Merope with the chain to show it to Bob Ogden and claim they're Slytherin's descendants, and presumably Merope wore it for most of her life in the Gaunt shack. Merope runs off with Tom Sr. wearing it and per Burke it's the last possession she had days before her death:

“It was brought in by a young witch just before Christmas, oh, many years ago now. She said she needed the gold badly, well, that much was obvious. Covered in rags and pretty far along... Going to have a baby, see. She said the locket had been Slytherin’s. [...] She didn’t seem to have any idea how much it was worth. Happy to get ten Galleons for it.“

And Voldemort's enraged when Hepzibah Smith claims Merope stole it and was simply too dense to know its worth (which Merope clearly did, could hardly miss it with Marvolo's behavior):

“I had to pay an arm and a leg for it, but I couldn’t let it pass, not a real treasure like that, had to have it for my collection. Burke bought it, apparently, from a ragged-looking woman who seemed to have stolen it, but had no idea of its true value —” There was no mistaking it this time: Voldemort’s eyes flashed scarlet at the words, and Harry saw his knuckles whiten on the locket’s chain. “— I daresay Burke paid her a pittance but there you are.... Pretty, isn’t it? And again, all kinds of powers attributed to it, though I just keep it nice and safe....” She reached out to take the locket back. For a moment, Harry thought Voldemort was not going to let go of it, but then it had slid through his fingers and was back in its red velvet cushion. “So there you are, Tom, dear, and I hope you enjoyed that!” She looked him full in the face and for the first time, Harry saw her foolish smile falter. “Are you all right, dear?” “Oh yes,” said Voldemort quietly. "Yes, I’m very well....” “I thought — but a trick of the light, I suppose —” said Hepzibah, looking unnerved, and Harry guessed that she too had seen the momentary red gleam in Voldemort’s eyes.

The red flash in his eyes staying long enough for Hepzibah to notice.

2. Location

It's the sole horcrux in a location related to his childhood in the orphanage, and the cliffside location evokes Azkaban's (the fortress on a tiny island middle of the North Sea) - a seaside cave you have to swim to reach, described as "a bleak, harsh view, the sea and the rock unrelieved by any tree or sweep of grass or sand".

(When Sirius writes via tropical birds post-Azkaban escape, Harry thinks he's somewhere with sunlight and “palm trees and white sand” where he can't imagine dementors surviving for long).

My theory's that while Tom may've been covering up a violent fight, what ruined Amy and Dennis's minds so they were "never right afterwards" was a too powerful memory wipe - like Crouch Sr.'s on Bertha Jorkins - so they can recall they went into a cave with Tom but nothing more; that could also be a relevant association, as Tom used Legilimency to erase his uncle's memories and send him to Azkaban.

It starts with a concealed entrance and a "blood ward", something normally outside/protecting a magical home (interestingly HBP begins with Dumbledore having entered the Gaunt shack threshold and cursed fatally by the ring horcrux, entering the blood wards of the Dursleys' house, and ends in him dying after the Cave-as-Gaunt-house-simulation), with "denser than normal” darkness inside.

A concealed chained "ghostly green" little boat glides over a "great black lake" to the center island - matching descriptions of the boatride across the Hogwarts lake to the castle for first-years, and a reference to the fact that Nerope never got to attend school.

The Emerald potion, which Harry first thinks is a lamp, emits a green glow through the cavern, similar to Slytherin common room descriptions (“underground room with rough stone walls and ceiling from which round, greenish lamps were hanging on chains” / "it’s under the lake, so the light’s all green.”)

3. Drink of Despair

The potion is, of course, a liquefied dementor, which is linked to Merope in several ways.

The echoes of Lily's murder Harry hears near the dementors and his rage at Sirius betraying her parallels the memory of Merope being killed by her family and Tom’s rage at seeing it in his uncle’s memories - Morfin betraying her secret to their father and sending Marvolo after her, Merope's wordless pleading with her brother and father, Morfin’s cackle of laughter, and Merope screaming as she’s about to be killed by Marvolo.

“D’you know what I see and hear every time a dementor gets too near me?” Ron and Hermione shook their heads, looking apprehensive. “I can hear my mum screaming and pleading with Voldemort. And if you’d heard your mum screaming like that, just about to be killed, you wouldn’t forget it in a hurry. And if you found out someone who was supposed to be a friend of hers betrayed her and sent Voldemort after her —” (POA)

“She likes looking at that Muggle,” said Morfin, a vicious expression on his face as he stared at his sister, who now looked terrified. “Always in the garden when he passes, peering through the hedge at him, isn’t she? And last night —” Merope shook her head jerkily, imploringly, but Morfin went on ruthlessly, “Hanging out of the window waiting for him to ride home, wasn’t she?” “Hanging out of the window to look at a Muggle?” said Gaunt quietly. [...] “Is it true?” said Gaunt in a deadly voice, advancing a step or two toward the terrified girl. “My daughter — pure-blooded descendant of Salazar Slytherin — hankering after a filthy, dirt-veined Muggle?” Merope shook her head frantically, pressing herself into the wall, apparently unable to speak. “But I got him, Father!” cackled Morfin. “I got him as he went by and he didn’t look so pretty with hives all over him, did he, Merope?” “You disgusting little Squib, you filthy little blood traitor!” roared Gaunt, losing control, and his hands closed around his daughter’s throat. Both Harry and Ogden yelled “No!” at the same time; Ogden raised his wand and cried, “Relashio!” Gaunt was thrown backward, away from his daughter [...] Ogden ran for his life. Dumbledore indicated that they ought to follow and Harry obeyed, Merope’s screams echoing in his ears. (HBP)

(HBP's also the book Harry gives a step by step graphic description of Lily's murder to Slughorn; while Voldemort re-enacts Merope's through the cave protections)

Dumbledore says Morfin gave a "full and boastful confession" - which Tom Jr. Legilimized Morfin to give, explicitly referencing the last time his uncle attacked Tom Sr. in retaliation for Merope’s attraction to him and gloated to Marvolo about it - "He was proud, he said, to have killed the Muggles, had been awaiting his chance all these years."

While Harry only wants revenge for his parents with no thought for himself vs. LV framing his uncle for his pureblood family blasting him off their family tree, LV certainly has additional rage for his mother, and also doesn't forget his mother's screaming/general despair in a hurry, creating the locket cave decades after viewing the memories.

The dementors' varying effect and imagery is linked with - despair and hopelessness, losing the will to survive, not eating, victims huddling and hiding their faces and pleading, weakness and fainting, etc. Sirius says Crouch Jr. in Azkaban was "screaming for his mother by nightfall. He went quiet after a few days, though... they all went quiet in the end... except when they shrieked in their sleep.”

Which is exactly Merope's state in the Gaunt house with her father and brother:

Harry realized that there was somebody else in the room, a girl whose ragged gray dress was the exact color of the dirty stone wall behind her. She was standing beside a steaming pot on a grimy black stove, and was fiddling around with the shelf of squalid-looking pots and pans above it. [...] She looked a little cleaner than the two men, but Harry thought he had never seen a more defeated-looking person.

“Good morning,” said Ogden. She did not answer, but with a frightened glance at her father turned her back on the room [...]

And [Marvolo] spat on the floor at Ogden’s feet. Morfin cackled again. Merope, huddled beside the window, her head bowed and her face hidden by her lank hair, said nothing.

“‘Darling,’” whispered Morfin in Parseltongue, looking at his sister. “‘Darling,’ he called her. So he wouldn’t have you anyway.” Merope was so white Harry felt sure she was going to faint.

and:

Instead, [Marvolo] jeered at his daughter, “Lucky the nice man from the Ministry’s here, isn’t it? Perhaps he’ll take you off my hands, perhaps he doesn’t mind dirty Squibs....” Without looking at anybody or thanking Ogden, Merope picked up the pot and returned it, hands trembling, to its shelf. She then stood quite still, her back against the wall between the filthy window and the stove, as though she wished for nothing more than to sink into the stone and vanish.

Harry was on his feet once more, refilling the goblet as Dumbledore began to scream in more anguish than ever, “I want to die! I want to die! Make it stop, make it stop, I want to die!” “Drink this, Professor. Drink this....” Dumbledore drank, and no sooner had he finished than he yelled, “KILL ME!”

Merope's completely nonverbal throughout the scene, other than her screams. The Gaunts homeschooled, so she didn't even get to attend Hogwarts as an escape, as Tom, Harry, and others did and barely got an education (referenced by the boat ride resembling the first years’ boatride to Hogwarts). And she would've been forced to marry her brother and have his children.

(Morfin's association near the dementors is also his father - "'He’ll kill me for losing his ring,’ he told his captors over and over again [...] And that, apparently, was all he ever said again.")

What we hear of Merope as she's pregnant is the complete opposite of the dementors.

Merope wanted to live desperately enough that she sold a family heirloom for basically nothing a week before her death - so she was certainly trying to get food. (Comparatively, Harry in HBP due to grief for Sirius was "lying on his bed, refusing meals, and staring at the misted window, full of the chill emptiness that he had come to associate with dementors" until Dumbledore's letter came.)

Both times, Merope is facing death - with the Gaunts, she's too hopeless to speak even while pleading as she’s about to be killed; while pregnant with Tom (the only time we do hear Merope speak, secondhand), despite having wandered destitute for months and despite freezing and starving in midwinter and in the painful process of dying in childbirth, she has the will to speak until her dying breath - expressing hope for her son's future ("I hope he looks like his papa"), to give her son a name, Mrs. Cole saying it seemed "so important to the poor girl" to name him.

It’s reminiscent of how staying in Grimmauld Place is far worse for Sirius than living in a cave and eating rats on the run is, and where looking out for Harry also keeps Sirius going and gives him a purpose. 12GP is likewise linked with Azkaban/dementors/death (elaborated on here).

Voldemort's awareness of all this is probably the best indication, among others, that he doesn't share Dumbledore's viewpoint that Merope chose to die; and his response to that would likely be very like Harry's about Sirius - that she didn't want to go at all.

“I don’t care. You can have it, I don’t really want it.” Harry never wanted to set foot in number twelve, Grimmauld Place again if he could help it. He thought he would be haunted forever by the memory of Sirius prowling its dark musty rooms alone, imprisoned within the place he had wanted so desperately to leave.

Voldemort is similarly haunted by the memory of Merope - but unlike Harry he craves the aspects of his family and pureblood society that killed his mother even as he resents it; wants the house, the heirlooms, to remake himself into the Heir of Slytherin, grasping at power but also any and all connection he has to family.

4. Death and Burial

The last part is the drinker collapsing in weakness after finishing the potion, the desperate thirst, and when they crawl to drink from the lake, the Inferi army of the dead dragging them to death by drowning in icy water.

Referencing the months Merope wandered London destitute, her death in childbirth, and burial in a pauper's grave.

In Greek myth, Charon ferries deceased souls in his boat across the rivers of the underworld (often the Acheron, the river of misery, in some sources a lake), and those without proper burials are left behind to haunt the world as ghosts.

Proper burials or lack thereof a recurring canon motif, Voldemort himself telling the forces against him in DH to "Dispose of your dead with dignity" and Azkaban has a mass graveyard of prisoners, buried by dementors instead of their family.

5. Kreacher

I assume this is the significance of Voldemort asking for a house-elf and his horrific torture of Kreacher, since LV has also considered humans disposable for decades and killed many for this task already (the Inferi).

Merope was the servant of the household, and there's the general implication of lifetime service/"slavery" to her family.

“But the villagers’ shock was nothing to Marvolo’s. He returned from Azkaban, expecting to find his daughter dutifully awaiting his return with a hot meal ready on his table. Instead, he found a clear inch of dust and her note of farewell, explaining what she had done [...] The shock of her desertion may have contributed to his early death — or perhaps he had simply never learned to feed himself."

LV also recreates this family dynamic into the Death Eaters - which he calls his “true family” and who are his slaves and call him Master.

"as [Kreacher] drank, he saw terrible things... Kreacher’s insides burned... Kreacher cried for Master Regulus to save him, he cried for his Mistress Black, but the Dark Lord only laughed" (DH)

LV potentially thinks of a house-elf as a being who "deserves it" "instead" (and is part of the establishment/property he thinks are his birthright. And it's telling of house-elves enslavement and isolation that the only people Kreacher can ask for to save him in the midst of it are his owners.)

The details are a bit unclear, but LV likely already tested the potion/other defenses before turning the locket into a horcrux; he used Kreacher to empty the basin of potion to place the finalized locket, as there's no backdoors to drinking it.

So LV leaves right after the locket is placed, not bothering to wait until Kreacher's dead and underestimates his ability to Apparate out - and considered him so insignificant that he didn’t remember who Kreacher is in OOTP despite using him for a very important plot to lure Harry, directly contributing to his downfall.

And, ironically, Regulus via Kreacher plays the role of "dutiful daughter/servant running off with the locket and leaving a farewell note explaining what he's done".