As someone with DID, I am asking you to take ‘fictive’ out of your ‘alterhuman’ definition. Please. It feels really disrespectful of my disorder and the clinical words we use pertaining to it. These are for alters only and do not belong under the ‘alterhuman’ umbrella. We have our own words for those, fictive is one word we use for an alter with traits/name/experiences of a fictional character, introject is another. This is very disconcerting as someone who needs this word to stay clinical.

Fictive was a word coined by the alterhuman/soulbonding/endogenic community. The clinical word is fictional introject. confirmation: LINK see the 4th paragraph of this answer.