Urza's Mine

{T}: Add {C}. If you control an Urza's Power-Plant and an Urza's Tower, add {C}{C} instead.

Grim Monolith

Grim Monolith doesn't untap during your untap step.
{T}: Add {C}{C}{C}.
{4}: Untap Grim Monolith.

Urza's Tower

{T}: Add {C}. If you control an Urza's Mine and an Urza's Power-Plant, add {C}{C}{C} instead.

Darksteel Citadel

Clock of Omens

Tap two untapped artifacts you control: Untap target artifact.

Sol Ring

Voltaic Key

Thran Dynamo

Mana Vault

Mana Vault doesn't untap during your untap step.
At the beginning of your upkeep, you may pay {4}. If you do, untap Mana Vault.
At the beginning of your draw step, if Mana Vault is tapped, it deals 1 damage to you.
{T}: Add {C}{C}{C}.

Mox Opal

Metalcraft — {T}: Add one mana of any color. Activate only if you control three or more artifacts.

Tolarian Academy

{T}: Add {U} for each artifact you control.

Unwinding Clock

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

Phyrexian Metamorph

({U/P} can be paid with either {U} or 2 life.)
You may have Phyrexian Metamorph enter as a copy of any artifact or creature on the battlefield, except it's an artifact in addition to its other types.

Emrakul, the Aeons Torn

This spell can't be countered.
When you cast this spell, take an extra turn after this one.
Flying, protection from spells that are one or more colors, annihilator 6
When Emrakul, the Aeons Torn is put into a graveyard from anywhere, its owner shuffles their graveyard into their library.

Urza's Power Plant

{T}: Add {C}. If you control an Urza's Mine and an Urza's Tower, add {C}{C} instead.

Karn, the Great Creator

Activated abilities of artifacts your opponents control can't be activated.
+1: Until your next turn, up to one target noncreature artifact becomes an artifact creature with power and toughness each equal to its mana value.
−2: You may reveal an artifact card you own from outside the game or choose a face-up artifact card you own in exile. Put that card into your hand.

Metalworker

{T}: Reveal any number of artifact cards in your hand. Add {C}{C} for each card revealed this way.

Voltaic Construct

Ugin, the Spirit Dragon

+2: Ugin, the Spirit Dragon deals 3 damage to any target.
−X: Exile each permanent with mana value X or less that's one or more colors.
−10: You gain 7 life, draw seven cards, then put up to seven permanent cards from your hand onto the battlefield.

Well of Knowledge

{2}: Draw a card. Any player may activate this ability but only during their draw step.

Planar Portal

{6}, {T}: Search your library for a card, put that card into your hand, then shuffle.

Ancient Tomb

{T}: Add {C}{C}. Ancient Tomb deals 2 damage to you.

Howling Mine

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