Evelynn, the Agony's Embrace

Assassin (This creature has flash. When it enters
the battlefield, you may have it deal damage equal its
power to target tapped creature you don't control.)
At beginning of your opponent's upkeep, you
may reveal Evelynn from your hand. If you do,
until end of turn, that creature loses all abilities
and must attack this turn if able. You can't cast
another creature spell than Evelynn this turn.
"You know you want me."