Cavern of Souls

As Cavern of Souls enters, choose a creature type.
{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast a creature spell of the chosen type, and that spell can't be countered.

Destructor Dragon

Flying
When Destructor Dragon dies, destroy target noncreature permanent.

Dragonlord Atarka

Flying, trample
When Dragonlord Atarka enters, it deals 5 damage divided as you choose among any number of target creatures and/or planeswalkers your opponents control.

Atarka, World Render

Flying, trample
Whenever a Dragon you control attacks, it gains double strike until end of turn.

Balefire Dragon

Flying
Whenever Balefire Dragon deals combat damage to a player, it deals that much damage to each creature that player controls.