It's Red not black but that point is irrelevant.

I don't especially like poison stuff so I'm going to let Turbo get the first word in. From what i see this could be troublesome to balance in some cases, especially in buildings, and melee servants are pretty much unable to go directly for her if they know about the second noble phantasm because then they are stick in essentially a giant poison bubble. Any masters who aren't directly powerful who get stuck in it are even worse off. But Noble phantasms are meant to be power so once again I'll leave turbo to this one.