[quote=@vancexentan]
While an interesting idea Phase I don't believe [@Phase Transit]that would be easy to incorporate into a roleplay to my knowledge there is no previous example like it the most is self sustainment like Archers, or Gilgamesh because he's Gilgamesh and that's how he likes to do things
[/quote]

Waver in Fate/Grand Order is an example of a pseudoservant, having let Zhuge Liang take over his spirit. However, not much of what or how he achieved this is ever revealed, so it is true that there isn't much precedent to go off of.