Tau, born intact, saw the healing properties the shards of the broken had. When she broke a finger, her father used the shards to rebuild it. she realized that the ones who were broken, cast away from her tribe, could be helped. the land of the shattered was covered in shards. She collected them and began to heal the broken, granting them permission to go to the land of the intact, or so she thought. her father saw the new faces in his tribe, and Tau told her father what she did to help. his reaction was nowhere near what she expected. He ordered the new faces to be smashed to pieces, so that they wouldn't corrupt the place. Tau tried to stop him, but was shattered in the process, and left in the land of the shattered. she had been wronged by her people; that's when she realized how corrupt being "whole" can be. so she set out on a journey with fellow shattered and gathered materials necessary to place a curse upon the ones who had wronged her and her people. The intact found out about this and tracked her down as she was getting the curse ready. They broke her more; she shouldn't have lived, and with the curse complete, the last thing she said before her soul left her body was "May you forever be cursed to roam mindless, and may you FEAST upon the corrupted souls you possess."
Patrick Smith's universe with little glass people. I guess this is my headcanon explanation on why intact ones get "possessed"
