Reflecting Pool

{T}: Add one mana of any type that a land you control could produce.

Sol Ring

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Command Tower

Witch-king of Angmar

Flying
Whenever one or more creatures deal combat damage to you, each opponent sacrifices a creature of their choice that dealt combat damage to you this turn. The Ring tempts you.
Discard a card: Witch-king of Angmar gains indestructible until end of turn. Tap it.