Oooh. This is a thing black can do, certainly. But this is an incredibly powerful effect for the cost. And splashable.

Throw out a couple of these and combat pretty much stops being a thing.

So maybe be cautious with this? Does a one-off sorcery fill whatever niche you need this for? It's a lot safer.

If not, then my final comment is the rarity - this is a splashy effect. Common aint sensible; I'd suggest rare.