SCP 035 Possessive Mask

When SCP 035 enters the battlefield, equip it to
a creature or return it to your hand.
At the beginning of your upkeep, put a -1/-1
counter on equipped creature. If you can't, you
get a poison counter.
Whenever SCP 035 becomes unattached from a
permanent, destroy that permanent.
{x}{p/b}{p/b}: Gain control of target creature
with mana value X. Attach SCP 035 to it.
Equip {1}{p/b}{p/b}