[DS] Pet theories to get out of system.

In the initial intro of 'Dark Souls' it is Anastasia of Astora, the (future?) firekeeper of Firelink Shrine, turning Oscar of Astora Undead. I think this might be the crime/sin she committed as 'blasphemy against gods' (as blasphemy doesn't have to be verbal and can be a deed), for which her tongue was cut.

Five Lords of Cinder map to five stages of grief all too well: Watchers as Anger, Aldrich as Bargain, Yhorm as Depression, Lothric as Denial and Ludleth as Acceptance.

Ludleth is pygmy lord from the Ringed City, directly or indirectly. There are numerous mentions that Ringed City-made Abyssal items "betrays a smidgen of life", and Ludleth is the guy who transpose the powerful souls into items via transposing kiln. Courland could be native name of the Ringed City or some other related land. The centre of the transposing kilt itself looks like an agglomeration of humanity or how hexes/dark spells usually portrayed, giving another connection to the Abyss.

Gwyndolin is Velka's child by most possibly Gwyn. Velka is the only DS1 goddess who grants miracle talisman that scales with Int (pardoners, her priesthood, in general seems to have a strong favour of Int over Faith). Gwyndolin is the only DS1 god who's soul holds sorcererous catalyst that scales with Faith – mechanically, he is a mirror of Velka, Faith-powered sorcery versus Int-powered miracles. Gwyndolin is also strongly associated with moon; Velka is called witch-goddess and witches are also strongly associated with the moon.
In addition, there is a possible connection through Painted World of Ariamis/Priscilla and Yorshka.
1) Painted World is littered with Velka's items (pardoner set, Velka's rapier, pardoner's miracle);
2) Both Priscilla and Velka are strongly tied to occult (hexes and dark-tinted items as they called in later games, type that gods are vulnerable to) and both Priscilla's Dagger and Velka's Rapier have occult damage, two out of three items to do so in DS1. Dark Ember (to occult-empower weapons) is also in the Painted World.
3) In DS3, Gwyndolin and another half-breed, Yorshka, are directly associated. It is tentative at best to link Yorshka to Priscilla – except both being sort-of-draconian halfbreeds, dressed in white and imprisoned in cold, hard to reach places, they are not all that similar, but still.

First Sin and Hollows of Londor: Gwyn, being a Lord of Light, is afraid of Dark and of the end of Age of Fire. Resisting the incoming fading of his Age, he linked multiplying humanity to the First Flame, intending to use sparks of Dark Soul within every human as a free fuel to renew the flame – both to powerup his Age of Fire and to subvert humanity for his cause and rule. He also sealed Abyss in the ring of fire, making a previously dormant realm way more aggressive and disturbed than it was ever supposed to be naturally. Humanity, or specks of Dark Soul within every human, were funneled into the First Flame through bonfires and Way of White was established to guide humans to this fate without scrutiny or rebellions as a way of religious manipulation. While there are many bonfires, it is special ones, guarded by firekeepers, that used as main nodes in what I see as some kind of network to bring humanities to the Kiln of the First Flame.

At first this scheme probably worked well but the demand of First Flame far outstripped the capability of humans to fuel it, even with their growing numbers: at first Undead and then Hollows started to appear. Undeath is probably the natural, 'dark' state of humanity, but I think the mindness madness in Hollowing is induced by linking of the humanity to the flames – First Flame sucks the Dark Soul/humanity out of undead, leaving only abyss-filled agitated carcass of Hollow; if not for the link, Undeath humans probably will be living the unnatural Undeath life without much troubles. Hollows are crazy in DS1 and DS2 but in DS3 Londorian Hollows are not. I think it is because Hollows of Londor, following the teaching of Darkstalker Kaathe, found a way to 'unlink' themselves from the First Flame, and hatch the whole 'usurpation of flames' plot, sort of doing in reverse what Gwyn did in the Age of Gods.

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The most unresolved mystery of all Dark Souls:  how did Yhorm manage to fit the doors into his own throne room? Even if to assume that he used the bonfire that appears after his death, it still was his throne room before he became the Lord of Cinder, so at some point of his life he had to go there in person, and I don't see any back doors or crumbled archways for a bigger gates.