Siv, Wizard of the Wastelands

Ward—Mill five cards.
Whenever Siv, Wizard of the Wastelands
becomes tapped, each opponent mills two cards.
Whenever an opponent mills an instant or
sorcery card, exile it from their graveyard and
put a +1/+1 counter on Siv.
When Siv dies, exile up to X target cards from graveyards, where X is Siv's power.