msem-instigator

Prowess
Whenever Unseen Hand attacks, exile target noncreature, nonland card with mana value 1 or less from your graveyard. Copy that card. You may cast the copy. (You still pay its costs.)

Discard a card: Unseen Maniac gets +1/+1 and can't be blocked this turn.
Whenever Unseen Maniac deals combat damage to a player, draw a card.

Target attacking creature fights another target attacking creature.

Glitch—Sacrifice a creature. (Remove one [restriction] for each time you pay the glitch cost.)
When Unshackled Revolutionary enters the battlefield, you may destroy target creature an opponent controls [with mana value 3 or less]. [You lose 3 life.]

Search target player's graveyard and library for up to one card each and exile those cards. That player shuffles.
Agonize (You may cast this card from your graveyard by putting a -1/-1 counter on a creature you control in addition to paying its other costs. Then exile this card.)

All creatures get -2/-2 until end of turn. Add {B}{B}.

Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)
Unstable Borer attacks each combat if able.

Reverberate {2}{R} (When you cast this spell, copy it if you paid its reverberate cost.)
Creatures your opponents control get -2/-0 until end of turn. If Unstable Experiment is reverberated, creatures you control get +1/+0 until end of turn.

Vanishing 2 (This permanent enters the battlefield 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.

You may have Unstable Impersonator enter the battlefield as a copy of any creature on the battlefield chosen at random.

Vanishing 5 (This permanent enters the battlefield with five time counters on it. At the beginning of your upkeep, remove a time counter from it. When the last is removed, sacrifice it.)
{1}{R}, Remove a time counter from Unstable Magmaling: Flip a coin. If you win the flip, it deals 3 damage to any target.

When Unstable Orb enters the battlefield, draw a card.
{3}, {T}, Sacrifice Unstable Orb: It deals 2 damage to target creature.

Rhapsody {4}{U}{U} (Pay {4}{U}{U} to cast this as a 4/4, or as a sorcery to make it become a 4/4.)
When Unstable Prophet enters the battlefield, surveil X, where X is its power. (Look at the top X cards of your library, then put any number of them into your graveyard and the rest on top of your library in any order.)

Whenever Unstable Vein enters or leaves the battlefield, choose one —
• Put a +1/+1 counter on each of up to two target creatures.
• Unstable Vein deals 2 damage to target creature with flying.

Menace
Unveil {3}{B}{R} ({3}{B}{R}: Transform this. Unveil only as a sorcery.)

Return target creature card from your graveyard to the battlefield with an additional -1/-1 counter on it.

Experience (Whenever this creature attacks, if it has fewer than three +1/+1 counters on it, put a +1/+1 counter on it.)
Unstoppable Weed gets +1/+1 for each +1/+1 counter on other creatures you control.

Return target creature to its owner's hand.

Choose one, then choose another for each card named Unsuspecting in your graveyard.
• You may return a permanent you control to its owner's hand.
• You may put an artifact, creature, or land card with mana value 2 or less from your hand onto the battlefield.
• Untap up to three target permanents.
• You gain 4 life.

Target creature you control gets +1/+0 until end of turn. That creature deals damage equal to its power to another target creature.

Whenever a land becomes tapped, its controller sacrifices it and creates a Treasure token.

Renown 1 (When this creature deals combat damage to a player, if it isn't renowned, put a +1/+1 counter on it and it becomes renowned.)
Whenever a creature you control becomes renowned, create a 1/1 red Soldier creature token with haste.

Flash
Deathtouch

{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.