🍁Nine Ancient Obelisks

outside of turn, dialogue-based RP?

Yes.

it's unknown whether he'll obey or not?

He will obey; there's no chance he won't. For example, it wouldn't have worked 100% on Ginzu.

will he listen to me, or will he "end up in the party" but continue to do strange things?

He won't become a Berserker (you'll be able to command him on the map like other creatures), but the details will depend on his character and the circumstances (i.e., it's not a mindless slave).