If we want to stick with the hardening, here's a precedent...
Cocoon (Ex): A thorciasid can eject a stream of noxious goo that hardens on contact, potentially fixing a subject in place and hindering its movement and actions. Using a standard action, the thorciasid makes a ranged touch attack against any foe it can see up to 60 feet away. If it succeeds at the ranged touch attack, the subject makes a grapple check against the cocoon. This is accomplished as if the thorciasid itself were making the grapple check with a competence bonus of +10, for a total check modifier of +37. On a failed check for the subject, the goo hardens into a partial cocoon, and the victim is treated as if grappled (even though the thorciasid is free to do as it desires). The subject can attempt to break the grapple of the cocoon (or use Escape Artist) each round, making an opposed grapple check against the cocoon (check modifier +37 for the cocoon).
A thorciasid can reinforce a partial cocoon by spending a standard action secreting additional goo. Each action so spent provides an additional +5 to the cocoon's grapple check modifier. Visually, the victim becomes more and more covered and is finally completely encased in a cocoon. Even fully encased victims can still breathe, and a thorciasid can drain a victim's life force at its leisure.
