Fictive

Fictives are headmates based on a fictional source. Common sources are media like games and books, but almost anything can be a fictive's source, such as original characters or D&D characters created by other system members.

Related Terms
Factives are headmates based on a non-fictional source, like another person.

Introject is an umbrella term for fictives that have a source.

Fictive-flux is when a headmate's connection to their source(s) varies over time.