Howling Mine

At the beginning of each player's draw step, if this artifact is untapped, that player draws an additional card.

Unwinding Clock

Untap all artifacts you control during each other player's untap step.

Mana Crypt

At the beginning of your upkeep, flip a coin. If you lose the flip, this artifact deals 3 damage to you.
{T}: Add {C}{C}.

Winter Orb

As long as this artifact is untapped, players can't untap more than one land during their untap steps.

Seat of the Synod

Jeweled Lotus

{T}, Sacrifice this artifact: Add three mana of any one color. Spend this mana only to cast your commander.

Lightning Greaves

Equipped creature has haste and shroud. (It can't be the target of spells or abilities.)
Equip {0}

Lotus Petal

{T}, Sacrifice this artifact: Add one mana of any color.

Sapphire Medallion

Blue spells you cast cost {1} less to cast.

Urza, Lord High Artificer

When Urza enters, create a 0/0 colorless Construct artifact creature token with "This token gets +1/+1 for each artifact you control."
Tap an untapped artifact you control: Add {U}.
{5}: Shuffle your library, then exile the top card. Until end of turn, you may play that card without paying its mana cost.