This is a card idea I've had floating around for a while. I think it's at the right level of power when in a set that could use the flavor. Other things I've thought of include black mana only for X, with a more powerful effect, and various different costs for the ability. It was intended originally for a cycle of XCC rares, but I've forgotten the others (they weren't particularly memorable)
Necrotic Spores
Enchantment
Necrotic Spores comes into play with X spore counters on it.
Remove a spore counter from Necrotic Spores, pay 1 life: All creatures get -1/-1 until end of turn. If there are no spore counters left on Necrotic Spores, sacrifice it.
