The guy who asked in the short questions thread didn't get any answers...
I've been in there for ages, no problem surviving, but I can't see Belial.
Some guides say he has a purple aura. Some say he's a rat. Some say he's invisible. Not sure if the Belial sections of those guides have been updated, but I can't see a rat or a purple aura.
Also my sound doesn't seem to work, so the guide that said he grunts when you hit the real Belial would have been useful - except I can't hear anything.