Wraiths

"After many years of ceaseless research and dedication, the mages of Estelore finally succeeded in opening a 传送门 of their own. A 传送门 which, they soon learned, had 否 destination. It went to a space 之间 worlds: an endless void. 来自 this void came creatures, beings of formless entropy and otherworldly vacuity that inhabited that plane of nothingness. They slipped through the 传送门 in the moments it existed and, being creatures of spirit rather than flesh, possessed the archmages of Estelore. Not a week passed before all on the island were under the creatures' dominion." – 《堕落冠军 II》: Public Design Document

Wraiths are creatures of the realms 之间, and can enter mortal realms mostly by incautious use of portals. They dont feel anything, and their driving force is seeking out 其他 creatures to devour their emotions, feelings, and the 偏好. If a wraith eats entities with sufficently strong feelings/emotions/etc, they might turn into... Something else