Doubling Cube

{3}, {T}: Double the amount of each type of unspent mana you have.

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.

Tarnished Citadel

{T}: Add {C}.
{T}: Add one mana of any color. Tarnished Citadel deals 3 damage to you.

Transmute Artifact

Sacrifice an artifact. If you do, search your library for an artifact card. If that card's mana value is less than or equal to the sacrificed artifact's mana value, put it onto the battlefield. If it's greater, you may pay {X}, where X is the difference. If you do, put it onto the battlefield. If you don't, put it into its owner's graveyard. Then shuffle.

Power Artifact

Enchant artifact
Enchanted artifact's activated abilities cost {2} less to activate. This effect can't reduce the mana in that cost to less than one mana.

City of Solitude

Players can cast spells and activate abilities only during their own turns.

Mox Diamond

If Mox Diamond would enter, you may discard a land card instead. If you do, put Mox Diamond onto the battlefield. If you don't, put it into its owner's graveyard.
{T}: Add one mana of any color.

Static Orb

As long as Static Orb is untapped, players can't untap more than two permanents during their untap steps.