Mirra, Jeskai Outcast

Flash
When Mirra enters the battlefield, distribute X
stun counters among any number of
target creatures.
{3}: Put a stun counter on target creature.
Creatures with stun counters on them can't
attack or block, and their activated abilities
can't be activated.
At the beginning of your end step, remove a stun counter from each creature with a stun
counter on it.