Filter! Thanks, everyone, that's great.
Norfleet, I tend to agree with Hong. I'm looking at adventure design from the point of view of the creatures who live in this cavern. They're all undead, and they don't need to breath, and they want to strongly discourage living interference; so what's the obvious choice? Making the atmosphere inhospitable is a good tactic that is consistent with their reasoning. If I eliminated any obstacle that the PCs could deal with, I'd be destroying the players' suspension of disbelief. Heck, do all doors suddenly become unlocked when the 3rd lvl wizard learns
knock?
In fact, it's even a good idea from a strategic level, because invaders trying to deal with this problem are going to require a spell (in this case a
limited wish or a
miracle, since the PCs don't currently know
Filter), and that's one less spell that is going to be aiding their attack.
You know, they actually thought about the globe of water/water breathing trick. They currently need to invade a ghoulish city within the next day, and they don't necessarily have all the resources they'd like; no necklaces of adaptation, nowhere to buy scrolls. They'll have to be inventive.
And Forceuser? They're already planning on using
avoid planar effects, but only to try and avoid the strong negative energy from this area, which may or may not work depending on what's causing it.
