Saya, The Innocent Horror

Hexproof
At the beginning of each combat, creatures your
opponents control get -X/-0 until end of turn
for each dementia counter they have.
{g}, {t} : Put a dementia counter on target
creature.
{u/b}{u/b}{6}, {t}, Exile Saya, The Inocent Horror:
Gain control of all creatures with a
dementia counter on it.