Oh, right. He should actually schedule some Alter Selfs to take place where he can see them.
Yaisa okay with doing that tomorrow? He probably won't date her tomorrow, but it doesn't has to be a date, just a quick switch where Keltham can see it.
Carissa wasn't created from scratch by the gods for Keltham; it's nearly certain that whatever force selected Keltham to arrive in this universe did so in a way that very strongly matched him and Carissa to each other, and selected Carissa for him to land on.
Keltham's got no idea if those forces explicitly negotiated with Asmodeus. Keltham would guess no on the explicit negotiations, but yes on Asmodeus and the other gods rapidly figuring out what was going on and making decisions that would've contributed to the tropes selecting this place for his landing, including some things that the gods would only do if the Keltham-steering forces looked to be sufficiently beneficial for them. Or if for some weird reason Asmodeus would've vetoed the whole thing if Keltham had landed on anybody who wasn't attractive to the Queen of Cheliax, then probably Keltham could've landed on Carissa at least in part for that reason; but the Keltham-steering forces might have needed to predict Asmodeus doing a lot in exchange to serve whatever goals Asmodeus was able to deduce predictably-to-the-steerers from seeing how Keltham had been steered already.
Negotiations like that don't have to be explicit when you're a god.
What's 'slave'? Keltham heard Yaisa use that term before and he can tell from context that it's a sex thing, but not the details.