Whenever a player casts a spell, that player may pay . If the player does, they draw a card.

Skulk (This creature can't be blocked by creatures with greater power.)

When Uninvited Geist deals combat damage to a player, transform it.

2 — : Add one mana of any color.

3 — Whenever this creature attacks, if it's not a Brushwagg, it gets +X/+0 until end of turn, where X is the number of supertypes, card types, and subtypes it has.

2 — 5/1

4 — 4/8

Support 2. (Put a +1/+1 counter on each of up to two target creatures.)

Untap each creature you control with a +1/+1 counter on it.

, , Sacrifice Universal Solvent: Destroy target permanent.

Unleash the Inferno deals 7 damage to target creature or planeswalker. When it deals excess damage this way, destroy target artifact or enchantment an opponent controls with mana value less than or equal to that amount of excess damage.

Search your library for a Doctor card, reveal it, put it into your hand, then shuffle.

When Unlucky Witness dies, exile the top two cards of your library. Until your next end step, you may play one of those cards.

Devoid (This card has no color.)

Target creature you control fights target creature an opponent controls. If the creature an opponent controls would die this turn, exile it instead.

At the beginning of each combat, double the power and toughness of each creature you control until end of turn.

It becomes night. Until end of turn, target creature gets +1/+0 and gains trample and "Whenever this creature deals combat damage to a player, draw a card."

Flashback (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Return target permanent card from your graveyard to your hand. Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Target creature gains haste until end of turn.

If a cycling ability of another nonland card would cause you to draw a card, instead exile cards from the top of your library until you exile a card that shares a card type with the cycled card. You may cast that card without paying its mana cost. Then put the exiled cards that weren't cast this way on the bottom of your library in a random order.

Cycling (, Discard this card: Draw a card.)

Enchant creature

When Unquestioned Authority enters, draw a card.

Enchanted creature has protection from creatures.

Defender

: Unruly Catapult deals 1 damage to each opponent.

Whenever you cast an instant or sorcery spell, untap Unruly Catapult.

When Unscrupulous Agent enters, target opponent exiles a card from their hand.

Equipped creature gets +3/+3 and has first strike.

Whenever a creature dealt damage by equipped creature this turn dies, you may exile that card. If you do, create a 2/2 black Zombie creature token.

Equip

Changeling (This card is every creature type.)

Whenever you or a permanent you control becomes the target of a spell or ability an opponent controls, counter that spell or ability unless its controller pays .

When Unshakable Tail enters and at the beginning of your upkeep, surveil 1.

Whenever one or more creature cards are put into your graveyard from your library, investigate. (Create a Clue token. It's an artifact with ", Sacrifice this artifact: Draw a card.")

, Sacrifice a Clue: Return Unshakable Tail from your graveyard to your hand.

Kicker (You may pay an additional as you cast this spell.)

Damage can't be prevented this turn. If this spell was kicked, it deals 5 damage to target player or planeswalker.

When Unstable Glyphbridge enters, if you cast it, for each player, choose a creature with power 2 or less that player controls. Then destroy all creatures except creatures chosen this way.

Craft with artifact (, Exile this artifact, Exile another artifact you control or an artifact card from your graveyard: Return this card transformed under its owner's control. Craft only as a sorcery.)

Enchant creature

Enchanted creature gets +3/+3.

At the beginning of the upkeep of enchanted creature's controller, put a -1/-1 counter on that creature.

2 — : Switch this creature's power and toughness until end of turn.

4 — Whenever this creature attacks, it gets +5/+5 until end of turn.

2 — 3/2

3 — 2/7

Trample

Champion a Treefolk or Warrior (When this enters, sacrifice it unless you exile another Treefolk or Warrior you control. When this leaves the battlefield, that card returns to the battlefield.)

Whenever a creature you control becomes blocked, it gets +0/+5 until end of turn.

Deathtouch

Whenever Unstoppable Slasher deals combat damage to a player, they lose half their life, rounded up.

When Unstoppable Slasher dies, if it had no counters on it, return it to the battlefield tapped under its owner's control with two stun counters on it.

Untaidake, the Cloud Keeper enters tapped.

, Pay 2 life: Add . Spend this mana only to cast legendary spells.

Kicker (You may pay an additional as you cast this spell.)

Vigilance, trample

If Untamed Kavu was kicked, it enters with three +1/+1 counters on it.

Trample

Other Wolves and Werewolves you control have trample.

: Put a +1/+1 counter on target creature.

Nightbound (If a player casts at least two spells during their own turn, it becomes day next turn.)

Trample

Whenever Untethered Express attacks, put a +1/+1 counter on it.

Crew 1 (Tap any number of creatures you control with total power 1 or more: This Vehicle becomes an artifact creature until end of turn.)

Destroy target creature. Its controller manifests dread. (That player looks at the top two cards of their library, then puts one onto the battlefield face down as a 2/2 creature and the other into their graveyard. If it's a creature card, it can be turned face up any time for its mana cost.)

Menace (This creature can't be blocked except by two or more creatures.)

, Exile Unwilling Ingredient from your graveyard: You draw a card and you lose 1 life.

: Regenerate Unworthy Dead.

Disguise (You may cast this card face down for as a 2/2 creature with ward . Turn it face up any time for its disguise cost.)

When Unyielding Gatekeeper is turned face up, exile another target nonland permanent. If you controlled it, return it to the battlefield tapped. Otherwise, its controller creates a 2/2 white and blue Detective creature token.

Target creature gains flying until end of turn.

Draw a card at the beginning of the next turn's upkeep.

Creatures played by your opponents enter tapped.

Creatures you control have haste.

Creatures your opponents control enter tapped.

When Urabrask's Anointer enters, it deals X damage to any target, where X is the number of permanents you control with oil counters on them.

Draw three cards. You may play an additional land this turn.

When Urbis Protector enters, create a 4/4 white Angel creature token with flying.

, Sacrifice Urborg Panther: Destroy target creature blocking Urborg Panther.

Sacrifice a creature named Feral Shadow, a creature named Breathstealer, and Urborg Panther: Search your library for a card named Spirit of the Night, put that card onto the battlefield, then shuffle.

Kicker (You may pay an additional as you cast this spell.)

: Regenerate Urborg Skeleton.

If Urborg Skeleton was kicked, it enters with a +1/+1 counter on it.

Each land is a Swamp in addition to its other land types.

Destroy target Spirit or enchantment.

Flying

Whenever Urgoros, the Empty One deals combat damage to a player, that player discards a card at random. If the player can't, you draw a card.

When Uro enters, sacrifice it unless it escaped.

Whenever Uro enters or attacks, you gain 3 life and draw a card, then you may put a land card from your hand onto the battlefield.

Escape—, Exile five other cards from your graveyard. (You may cast this card from your graveyard for its escape cost.)

Whenever you cast a Myr spell, create a 1/1 colorless Myr artifact creature token.

At the beginning of combat on your turn, untap each Myr you control.

, : Put three +1/+1 counters on each Myr you control. Activate only during your turn.

+1: Head to AskUrza.com and click +1.

-1: Head to AskUrza.com and click -1.

-6: Head to AskUrza.com and click -6.

When Urza, Lord High Artificer enters, create a 0/0 colorless Construct artifact creature token with "This creature gets +1/+1 for each artifact you control."

Tap an untapped artifact you control: Add .

: Shuffle your library, then exile the top card. Until end of turn, you may play that card without paying its mana cost.

Vigilance

, : Draw a card, then discard a card.

Whenever you discard one or more artifact cards, create a tapped Powerstone token. This ability triggers only once each turn. (The token is an artifact with ": Add . This mana can't be spent to cast a nonartifact spell.")