Mist from the Apocalypse

Flying, trample
"Tragedy was slain, but it's spirit lives on in the rubble. In every cloud of smoke on Innistrad, she is seen drifting. In every pale, starless nighttime sky, she is watching. Her writhing, eldritch flesh grips every corpse she left on the fallen plane. She is memorialized not in stone, not in memory, but in fear."