msem-instigator

If you would draw one or more cards, draw that many cards plus one instead.
When Unleashed Mindboggler dies, return it to the battlefield (front face up).

Conjure six duplicates of target instant or sorcery card in a graveyard into your main library. Then shuffle.
Draw a card.

{G/W}: If Unlikeliest Heroes doesn't have a +1/+1 counter on it, put a +1/+1 counter on it.
{2}{G/W}{G/W}: If Unlikeliest Heroes has a +1/+1 counter on it and doesn't have vigilance, put two +1/+1 counters and a vigilance counter on it.
{3}{G/W}{G/W}{G/W}: If Unlikeliest Heroes has vigilance and not indestructible, put four +1/+1 counters and an indestructible counter on it.

{T}, Pay 1 life: Add {U} or {B}.
{1}, {T}, Sacrifice Unlit Alley: Investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

When Unmarked Vials enters, create a Vial token. (It's an artifact with “{1}, Sacrifice this and another permanent: Draw a card. Activate only during your turn.”)
{1}, {T}: Add one mana of any color.

When Unmasker of Fate's Design enters, look at target player's hand. Choose a nonland card from it and exile that card with a puzzle counter on it. As long as that card has a puzzle counter on it, that player may pay {2} and 1 life at any time. If they do, return the exiled card to their hand.

Draw two cards, then discard two cards.

Draw a card. If this spell was foretold, instead surveil 2, then draw two cards.
Foretell {2}{U} (During your turn, you may pay {2} and exile this card from your hand face down. Cast it on a later turn for its foretell cost.)

Flying
When Unraveller of Mysteries enters, mill two cards.

Vanishing 2 (This permanent enters with two time counters on it. At the beginning of your upkeep, remove a time counter from it. When the last is removed, sacrifice it.)
{T}: Add {C}.
When Unstable Footing is put into your graveyard from the battlefield, if it had no time counters on it, search your library for a basic land card, put it onto the battlefield, then shuffle.

Return target creature to its owner's hand.

{T}: Target attacking or blocking creature gets +1/+1 until end of turn.

{T}: Add {C}.
{T}, Sacrifice Untethered Spire: Choose target land card in your graveyard that was put there from the battlefield this turn. Return that card to your hand.

Untrekked Territory enters tapped.
{T}: Add {B} or {G}.
When Untrekked Territory enters, you may put a loyalty counter on a planeswalker you control.

Unvirtuous Maestro can't be blocked except by three or more creatures.

Unzari Ruins enters tapped.
{T}: Add {C}.
Tap five untapped creatures you control: Unzari Ruins becomes a 10/10 Construct artifact creature with trample until end of turn. It's still a land.

({T}: Add {B} or {R}.)
Urban Wastelands enters tapped.
Cycling {2} ({2}, Discard this card: Draw a card.)

Menace

Counter target noncreature spell unless its controller pays {1}. If there are four or more counters among creatures you control, counter that spell instead.

({T}: Add {B} or {R}.)
As Vacated Bar enters, you may pay {1}. If you don't, Vacated Bar enters tapped.

Melee (Whenever this creature attacks, it gets +1/+1 until end of turn for each opponent you attacked this combat.)
When Vaeldan's Liberator dies, you may exile it. If you do, return a permanent card with mana value less than or equal to Vaeldan's Liberator's power from your graveyard to your hand.

When Vale Ruins enters, you gain 1 life.
{T}, Sacrifice Vale Ruins: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Valley Falls enters tapped unless you control two or more white and/or blue permanents.
{T}: Add {W} or {U}.

Choose one—
• Prevent all damage that would be dealt by creatures without flying this turn.
• Prevent all damage that would be dealt by creatures with flying this turn.

Creatures you control get +1/+1 until end of turn.
Inscribe {2}{W} ({2}{W}: Exile this card from your hand inscribed on a creature you control. Whenever that creature attacks, its controller may cast a copy of the inscribed card without paying its mana cost. Inscribe only as a sorcery.)