No, in the name of all that's holy and not necromantically animated, I beseech thee to make no such creature, lest the world be overrun with swarms of undead body the likes of which the world should never know!
....You're totally gonna do it now, aren't you?
Anyway, I'm really tempted to give this an Mitp vote: no *+3 haterbane throwing dagger bounces off force field from bracers of armor* because of the uncomfortable amount of undead and otherwise irredeemably evil creaures that seem to be going into MitP. The swarm itself is yet another mechanically and creatively excellent creature in its own right, but I would really love to see more creatures that could be beneficial to players in a respect other than experience. However, because of the fact that it's a flavorful and creative irredeemably evil mockery of life's creation, I'm going to stay neutral.