Status Ward materia can be found in multiple missions. If you equip it, you will be immune to any status ailments that your equipped Materia can cause. Note: This works for the Dark and Hell Materia, such as Dark Blizzard or Hell Firaga. If you combine a Hell Materia with a Status Ward Materia, you will be immune to the following: Silence, Poison, Stop, and Death. It works very well in the latter missions.