I'm approaching the level where I may be able to pick up Mass Suffocation, but I'm not sure if I'm reading it correctly: One way seems worth a 9th level spell and one does not. If the target makes the initial fortitude save is he only staggered for 1 round and then free of the spell or would he continue needing to make saves for the duration, meaning that even if he keeps making it he is at the very least continually staggered?
If the Mass Suffocation can at the very least stagger one person per 2 levels for rounds per level without a save then I'd call it a good 9th level spell and the possibility of flat out killing them is just a bonus.
If you make the save you are only staggered, and then you are free. If you fail then you must continue to make for saves for the following rounds.
edit: Yes I know staggering someone is a good consolation prize.
That's what I was afraid of and it's disappointing; a single round of stagger actually seems like a pretty bleh consolation prize for a 9th level spell. On to the "not worth the expenditure" pile goes Mass Suffocation. I was actually considering it for the long duration stagger (and if it doesn't do that...) as it's not like anything meaningful is actually going to fail the fort save and die, especially if one initial success negates.
There are many spells of that level that are far more useful.