[RPGeek]

Let's see. He and Yxonumei (or whatever, I haven't played IWD for a long time) are enemies. Yxonumei is a Marilith (Tanar'ri).
That would automaticly assume that Balhilfet is a Lawful Evil Baatezu-Devil Pit Fiend, but wait! If he is a pit fiend, then how can he have been excluded, like he says he is?
After all, the Pit Fiends are vastly powerful monsters, who cannot be overcome by any other denizens of The Nine Hells. So where does this lead? Balhilfet isn't a Baatezu, but an exluded something-else. Perhaps he was an excluded underling of Yxonumei who made a pact with the Baatezu!
Or perhaps....
he isn't!
UWA HA HA!