Kerrigan, Queen of Blades

Swarm Leader — At the beginning of combat on
your turn, put a +1/+1 counter on target
creature
Psychic Stimulus — {t}: Add {c}{c}. When you
next cast a spell with {x} in its mana cost or
activate an ability with {x} in its activation
cost this turn, copy that spell or ability. You may choose new targets for the copy.
"Slay them all"