Board Thread:Dark Souls II/@comment-2.223.169.191-20140325204725/@comment-16047389-20141119174110

Personally, I believe that the Lost Sinner is actually Magus Eygil, creator of the Fire Snake and the Dance of Fire Pyromancies. Here's my reasoning:


 * First off, the door you find right behind the Lost Sinner after the fight is the exact same door design that you have to open to enter the Iron Keep, once you cross the bridge. This means that the Sinner's Rise and the Iron Keep share a common architect, and probably even built around the same times. Wheter or not the Sinner's Rise was built at the same time as the Lost Bastille, or slightly afterwards, is a different matter.


 * The Lost Sinner is resistant to Fire damage, and wears handcuffs that increase the power of Pyromancies. Magus Eygil was a powerful Pyromancer, and some of their power may have seeped into the handcuffs, the equipment closest to their Pyromancy Flame.

Here's how I think it all happened. Magus Eygil possessed the Old Witch Soul in addition to her own (whether this is because she was the direct reincarnation or simply found the soul, I don't know). With it, came a more in depth knowledge of Pyromancy. We know that the Curse of the Undead had begun to crop up around this time, meaning the First Flame was waning and once again required a powerful undead to relink it. Or did it? Perhaps, Magus Eygil thought, it could be relit without the need of offering a powerful soul. Surely she could use her Pyromancy to relight the First Flame. If you look closely at the floor where you fought Raime, you can see what appears to be the signs of all the ashes emenating from a central point. Much like in the Kiln of the First Flame in Dark Souls where you fight Gwyn. Perhaps the First Flame, or their attempt of recreating it, once stood there. The attempt, of course, failed as history has proven that it would. The result instead would be the firey Smelter Demon we find in the Iron Keep (although now we know that it is very likely that the Smelter Demon of the Iron Keep used to be like the one in the Iron Passage of Brume Tower, a puppet of the Old Iron King), who cast the Old Iron King into the lava below, where he would meet the one who's name must never be repeated, and become Ichorous Earth (or the vessel of it anyway). This would be the Lost Sinner's sin. In an attempt to relight the First Flame, she would effectively kill her own king, and doom her kingdom to ruin.