Garavak, Insane Necromance

When Garavak, Insane Necromance enters the battlefield, you may return target creature with converted mana cost of 4 or less.
{1}{b}, {t}, Amass 2
{x}{b}{b}, {t}, Amass X
Zombies you control have Trample and Haste.
When the going gets tough, the tough turn to
necromancy...