Why did Seymour's mother become such a horrific, grotesque looking aeon?
This is all speculation and I could’ve sworn I read something about this somewhere..
I think the major factors that it’s been influenced have been Jung’s personality theory, which you can read more about here and the Roman Catholic ‘Anima Sola’, which pictures as a soul in purgatory, having chains binding her wrist, which when broken has meant that she’s repented for her sins.
Combining this with something to do with her being so desperate to give her son some semblance of a normal life that in doing so, she became chained by it. Plus feelings about her own internal pain and struggle of not being able to do so combined with some many other factors (her illness, her marriage to Jyscal, the banishment, etc.) probably had something to do with it too.
The Jungian personality theory and the other religious meanings that are tied into her aeon design actually fit in quite well to the overall religious tones (plus a few minor ones) of the game itself.