Stone Nightmare

Indestructible.
Whenever a player casts a non-black spell, tap Stone Nightmare unless you pay {1}.
Nocturnal - At the beginning of your end step if Stone Nightmare is untapped, Stone Nightmare loses indestructible and becomes a 5/5 black Nightmare Horror creature with fear until the end of your next turn. (It cannot be blocked except by artifact creatures and/or black creatures.)