On the merc group...
I'm sure that the three of them would be glad to travel some with Chrysta, I'm sure. Rain, being the leader, might not like it, but who's she to stop a person from simply following them everywhere? I wonder if Chrysta would feel uncomfortable around Marda... she is, after all, a devout of a dark goddess and a widely renowned killer, even if she is rather friendly to everyone. As for Nemo... I have no idea how that would go. The three of them are a strange bunch... very outlandish and traumatizing to Pastor Dan and Mother Layna (heehee) I'm sure. If her parents found out she ran off with a serial killer (aka Marda), an impious bitch (Enter, Rain), and a living spell (ala Nemo), they'd have conniptions! Muahaha!
You know... Essie might have a long lost uncle, or something like that: It would be neat to find some of Chirion's family: He actually is out of touch with his family, and he'd likely seek them out to reconcile himself to them, or at the very least save them from some catastrophe, or save her from a bandit or something... could be neat.
With your siren-ish charachter, Chirion might have killed a few of those people in his days as a warlock, and might want to do something to make all that up, or try like hell to do so. Or, alternatively, the two might chance-encounter. I have an idea of some way they'd meet like that. Another possibility.
The slaver... I can see Chirion not liking her too much. He wouldn't attack her, I don't think, she's not really evil, just kinda devious... Could be a fun interaction... He's scaring away customers! (hee) Perhaps, again, he'd killed someone in her family or something like that. Thats how most of his interactions with people will start, it seems like.