Kennen, Keeper of Balance (Rare)

[Hidden] (Hide now for :rb_rune_rainbow: to react with later for :rb_energy_0:.)
When you play me or I attack, you may pay :rb_energy_2: to [Stun] a unit. (It doesn't deal combat damage this turn.)
While there's a stunned enemy unit here, I have +2 :rb_might:.