Leeching Nightmare

Lifelink
Nightmare {1}{b}{g} — You may tap this and/or any untapped creatures bound to it. Mill two cards for each creature tapped this way. (You may bind this creature with
up to two other creatures as they enter the battlefield and if they have nightmare. They remain bound for as long as you control them.)

Whenever Leeching Nightmare attacks, mill a card.

Whenever you mill a creature card through Leeching Nightmare, put a +1/+1 counter on target tapped creature you control.