Grid Monitor

Sol Ring

Steel Golem

Command Tower

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

Rust Elemental

Flying
At the beginning of your upkeep, sacrifice another artifact. If you can't, tap this creature and you lose 4 life.

Reliquary Tower

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

Arcane Signet

Zedruu the Greathearted

At the beginning of your upkeep, you gain X life and draw X cards, where X is the number of permanents you own that your opponents control.
{U}{R}{W}: Target opponent gains control of target permanent you control.