Swimmer in Nightmares

Swimmer in Nightmares

Creature - Nightmare Merfolk | Power/Toughness: 1 / 4 (CMC 3)
Swimmer in Nightmares gets +3/+0 as long as there are ten or more cards in a single graveyard.
Swimmer in Nightmares can't be blocked as long as you control an Ashiok planeswalker.