Concentrate

Mana Leak

Counter target spell unless its controller pays {3}.

Return target creature to its owner's hand.

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

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

Destroy all creatures. They can't be regenerated.

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

Return target permanent to its owner's hand.

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