Backing up, though the spell requires some maintenance, Snape stands shoulder-to-shoulder with the other woman, anything like creative banter lost in the silver light of the doe.

Lank hair whipping about his face with the force of that things breath-- if it can be called that -- he grimaces, but does not lose the doe, nor the memory.

At the very least, it breaks the tide of madness creeping forth... the rest is all on her barrier, and her strength. He can save their minds, but only she can really keep their flesh whole.