Command Tower

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

Exotic Orchard

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

Alistair, the Brigadier

Whenever you cast a historic spell, create a 1/1 white Soldier creature token. (Artifacts, legendaries, and Sagas are historic.)
Whenever Alistair attacks, you may pay {8}. If you do, creatures you control get +X/+X until end of turn, where X is the number of historic permanents you control.

Arcane Signet

Seaside Citadel

Seaside Citadel enters tapped.
{T}: Add {G}, {W}, or {U}.