I know both use honey select but... possible once in a lifetime cameo?
Yes, it's an OIALT cameo. If you've noticed, Caribdis is a patron of Jestur. You can see that at the end of the game when all the patrons are listed (or at least the major ones), Caribdis' name is there.
Or if I'm getting it wrong and he's not a patron, in any case he's an important supporter to Jestur.