Serra Angel can only be killed by these prominent 93-94 cards: a large blocking flyer, Psionic Blast, Fireball, Swords to Plowshares, Terror, Balance, Chaos Orb, Wrath of God, and Nevinyrrals Disk
Wort, Boggart Auntie can make great use of this, too, thanks to both her ability and the sacrifice subtheme associated with Goblins
These are what players tend to call "rare bombs," cards that allow the person who cast them to have a huge advantage toward winning the game
When they take damage you get to deal 3 damage to target opponent
I included three counters that counter target spell and bounce something at the same time quite ably - Lost in the Mist, Cryptic Command, and Very Cryptic Command
They both start as 3/3s that get +1/+1 counters whenever you discard a card or draw a card, respectively