poison - do you mean in the forgotten crypt with the troll talking about traps? you just jump up the platforms there and the lever to shut it off is at the top, although if you made it to the academy already, you would have gotten past that part already?
helmet - yes, there is only 1 path that leads downwards in the academy, go to the far end of the room down there and an undead pops out of the ground kill him and loot the helmet, you won't be able to collect the orbs or even get down to the rune area without the helmet.
