Not sure if anybody else has had this happen, but after slaying the Green Hag in her lair and saving the girl, when the "X Approves" messages all popped up, one of the messages said something along the line of: UNDEFINED APPROVES, implying there's another companion somewhere in the code that wasn't complete for Early Access.
I would still be happy if we only had these five to choose from, as I find them good enough characters (both mechanically, and in terms of writing), but I'm definitely hoping we get a Tiefling in our party considering the many obvious links to Descent into Avernus they've shown us so far. At the very least, having a Barbarian or Paladin companion (if and when those classes are added) would help the cast feel a bit more rounded out--currently Laezel is the only melee/tank option we have. I love Wyll, but he's far too squishy to carry that kind of a role...
