Hags

A hag is a person (male or female) who has struck a deal with the Mother Tree, replacing their heart (metaphorically and literally) with a seed of that corrupt entity. They gain drastically extended life and magical power in exchange for being dependent on the tree. Specifically, each hag is obsessed with one particular emotion or action, usually a negative one. Envy, strife, gossip, pain (causing or feeling), despair. Each one grants different powers, but the hag must wallow in that emotion constantly. If they don't, the seed shrivels up and dies, killing the hag. And if they sate themselves and find release from whatever caused this obsession...the seed sprouts and they become a daughter tree, cursed to sentient malevolence eternally.

Note that hags do not have to physically travel to the Hagfen--the tree magically reaches out to those that are in extremis or deep in obsession, offering power in exchange for service.