Arcane Signet

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

Field of the Dead

This land enters tapped.
{T}: Add {C}.
Whenever this land or another land you control enters, if you control seven or more lands with different names, create a 2/2 black Zombie creature token.

Command Tower

Reliquary Tower

You have no maximum hand size.
{T}: Add {C}.

Sol Ring

Prismatic Vista

{T}, Pay 1 life, Sacrifice this land: Search your library for a basic land card, put it onto the battlefield, then shuffle.

Fellwar Stone

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