Darksteel Ingot

Indestructible (Effects that say "destroy" don't destroy this artifact.)
{T}: Add one mana of any color.

Dimir Signet

Orzhov Signet

Alloy Myr

Arcane Signet

{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.

Azorius Signet

Thought Vessel

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

Sen Triplets

At the beginning of your upkeep, choose target opponent. This turn, that player can't cast spells or activate abilities and plays with their hand revealed. You may play lands and cast spells from that player's hand this turn.