ToME WikiRavenRed: Just a quick idea.
Noxious Cloud is... well... a cloud. More accurately, it's a lasting area-affect spell. At low levels this is quite a powerful effect. To modify this slightly, I'd change the effect below level 25 (on the T3 100-pt scale) to a "wave" effect, only changing to a cloud proper above level 25.
This makes its use somewhat trickier at lower levels, as it becomes a dynamic area of effect rather than a static one, requiring some strategic consideration from the player.
2c worth and counting...
ElCuGo: Noxious Cloud is relatively useless as it is, I don't think it needs to get even more underpowered.
RavenRed: I'd respectfully disagree. I believe it's the pre-eminent group attack spell. Given that it applies this damage every turn for its duration and that it affects even posion-resistant monsters at higher levels I think it's quite powerful in T2. In T3, however, the new poison system makes it even moreso.
ElCuGo: I haven't played T3, but in T2, once you enter Angband Noxious Cloud is not really that useful except for the initial ball damage and a lot of high level monsters are immune to high level NoxCloud. I agree that at low levels Noxious Cloud is pretty nice though.
DanielFishman: The thing about Noxious Cloud is that it does a lot of damage for the amount of mana it uses - which is particularly important at low levels. It doesn't do as much damage per turn as Manathrust or Fireflash, but you can toss one at the entrance to an orc pit and just press 5 until they're all dead. Once you get into Mordor it starts fading out as the damage isn't high enough to take out anything that uses melee, and you can't afford to wait for it to kill off a spellcaster or breather. (this is from experience playing Sorcerers, rather than Mages or Geomancers though). I'm not sure that it needs changing though.