Assault Suit
Equipped creature gets +2/+2, has haste, can't attack you or planeswalkers you control, and can't be sacrificed.
At the beginning of each opponent's upkeep, you may have that player gain control of equipped creature until end of turn. If you do, untap it.
Equip 
Illustrated by Games Workshop
This printing
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If an effect instructs you to sacrifice a creature, and you control any creatures other than the creature equipped with Assault Suit, you must sacrifice one of them. You can't try to sacrifice the equipped creature, fail, and therefore ignore the effect.
The equipped creature can't be sacrificed for any reason. If an effect instructs you to sacrifice it, you can't and it remains on the battlefield. You also can't sacrifice it to pay a cost that requires you to sacrifice a creature.
