Ultros, Obnoxious Octopus {1}{U}

Whenever you cast a noncreature spell, if at least four mana was spent to cast it, tap target creature an opponent controls and put a stun counter on it. (If a permanent with a stun counter would become untapped, remove one from it instead.)

Whenever you cast a noncreature spell, if at least eight mana was spent to cast it, put eight +1/+1 counters on Ultros.