The players will be on a small open area, with a small house, in the middle of a ancient forest.
They will interact to a mute man (spined devil) and his small dog (nessian warhound). The man will call his "wife" (Rakshasa) and pcs will be forced to attack her (by a powerful magical mean), but she will attack them too, so it's not gonna be a surprise...
...except that the man an his dog changes back to their devil appearance, female rakshasa not. Dog will be tanking, spined devil will fly and ranged attack and the rakshasa will spend her first round climbing to small house's roof then start casting spells.
There's a reason these two devils are there with her, so I'd like to keep them, although hellcats and imps could do it better...