Ymior's Legacy

When Ymior's Legacy enters the battlefield, take control of target creature for as long as you
control at least two Ethers.
Ethers you control get +1/+1 for each creature
you control that you don't own.
{6}{b}{b}, Sacrifice a creature: Take control of
target creature indefinitely. This ability costs {1} less to activate for each Ether you control.