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.
Ashiok's minions plumb the depths of the ocean and the psyche.
NM-Mint - $0.50
Lightly Played - $0.45
Moderately Played - $0.40
Heavily Played - $0.35
Damaged - $0.25
NM-Mint Non English - $0.50
Lightly Played Non English - $0.45
Moderately Played Non English - $0.40
Heavily Played Non English - $0.35
Damaged Non English - $0.25