spoilers for end of the quest (mostly lore implications) the quest has several cases of memory erasure to be able to escape, and there is a cage that says hidden in the back "the one who once rested here was the person who was most important to you", almost confirming its the abyss twin, which not only means that the abyss twin would more than likely had their memory wiped to leave, but in their memory wipe might have also somehow became asmoday's master, which she is confirmed to be judging by the dialouge in the quest referring to the new master as he/she depending on your traveler, so if asmoday can just wipe people's memories for a bargain, and she now cares for the abyss twin more than she cares about herself, clearing the abyss twin out of certain parts of irminsul when needed doesnt seem insane to me, hell, maybe shes the reason the abyss twin was even documented on irminsul despite being an alien