Yap-Yap, The Destroyer

When Yap Yap, The Destroyer enters
the battlefield create Throne of Woe a Legendary Artifact token with Hexproof and "Whenever a
player casts a spell you and target opponent create
X 1/1 Grunt Goblin Monkey creature tokens
where X is equal to the mana value of the casted
spell."
If Throne of Woe is destroyed sacrifice Yap Yap,
The Destroyer.