Fellwar Stone

{T}: Add one mana of any color that a land an opponent controls could produce.

Braingeyser

Serra Angel

Island

Sol Ring

Plains

Divine Offering

Destroy target artifact. You gain life equal to its mana value.

Tundra

Serendib Efreet

Flying
At the beginning of your upkeep, Serendib Efreet deals 1 damage to you.

Mana Short

Tap all lands target player controls and that player loses all unspent mana.

Savannah Lions

Power Sink

Counter target spell unless its controller pays {X}. If that player doesn't, they tap all lands with mana abilities they control and lose all unspent mana.

Counterspell

Mishra's Factory

{T}: Add {C}.
{1}: Mishra's Factory becomes a 2/2 Assembly-Worker artifact creature until end of turn. It's still a land.
{T}: Target Assembly-Worker creature gets +1/+1 until end of turn.

Psionic Blast

Psionic Blast deals 4 damage to any target and 2 damage to you.

Strip Mine

{T}: Add {C}.
{T}, Sacrifice Strip Mine: Destroy target land.

Disenchant

Swords to Plowshares

Exile target creature. Its controller gains life equal to its power.