Simple Q&A for Pathfinder 3: Find With a Vengeance

[Karoht]

A10
The rules on sleeping are vague, and it has always been ambiguous on whether elves sleep or not. I assume the same goes for Drow.

But say if you are playing a setting that allows to trance rather then sleeping, it is something you need to work out with your DM. The precise line is "If the summoner is unconscious, asleep, or killed, his eidolon is immediately banished" and most likely trance doesn't fall under asleep or unconscious (or killed for that matter), so it is logical that the eidolon sticks around. But your DM ruling may very.

A10: Addendum
I could see an argument via the DM that the answer is no, just based on the idea that a Synthesist could be in demon mode 24/7 by that logic. So be sure to clarify with your DM if you are or are not going to be a Synthesist if you want to make the argument that trance should work and keep the Eidolon active.