If the affected character (or creature) fails to save vs. poison, he immediately suffers the effects similar to a temporal stasis spell, and an ice-like glaze forms over his body. Neutralize poison or a similar spell negates the effect, as does certain herbal treatments known by some Ulutiun healers.
Ok, do we really want to base the poison on temporal stasis? That's a pretty powerful effect for such low HD critters. Then again, I guess it's not to hard to remove.
It sounds like we could go for cold damage as well. Is there a precedent for freezing solid?
Well we could base the effects on a similar but lower level spell instead, namely sepia snake sigil.
Maybe the "suspension" effects only last as long as the ice crust does, so the frozen victim returns to normal if they're attacked so the ice breaks? That'll still be useful as a defense but removes some of the more exploitable elements. Shorten the duration to a few rounds and bob's your uncle.
I like where this is headed, but would prefer warming a victim up to release them, rather than attacking them. I see it more as a rimy crust than being encased in ice.