From Pluralpedia, the collaborative plurality dictionary
obsessor (n., adj.)
Applies toheadmates
Coinerthe unconscious

An obsessor is a headmate whose purpose is to obsess over something or someone. For the coiner, it's usually because of a FP, but it is not BPD specific.

The term was coined by the unconscious/lyre system here and on Tumblr.

Please do not use this term if you are not Traumagenic, as the coiner has asked endogenic, tulpa and demo systems not to use it