Kennen, Heart of the Tempest

When Kennen enters the battlefield apply a stun counter to target creature. If target creature already has a stun counter, deal 2 damage to it instead.

Level up (When you've summoned the same creature 5 times, grant Kennen +1/+1 and "When Kennen enters the battlefield, blocks, or attacks, apply a stun counter to a target creature. If target creature already has a stun counter, deal 2 damage instead.")