Insidious Order

Manipulation: Tap an untapped creature you
control. (Tap an untapped creature you control: Put
a control counter on Insidious Order. You may remove
X control counters from Insidious Order. If you do,
you gain control of target creature with toughness X or
less. Activate this ability only as a sorcery.)

Whenever you gain control of a creature your opponent's own, you become the monarch.

"May he reign eternal."