Boomerang

Return target permanent to its owner's hand.

Air Elemental

Whenever City of Brass becomes tapped, it deals 1 damage to you.
{T}: Add one mana of any color.

Search target opponent's library for a creature card and put that card onto the battlefield under your control. Then that player shuffles.

Counter target spell unless its controller pays {3}.

Coastal Tower enters tapped.
{T}: Add {W} or {U}.

Return target creature to its owner's hand.

Destroy all creatures. They can't be regenerated.

Flying
Vigilance (Attacking doesn't cause this creature to tap.)