msem-instigator

When Unite Against Evil enters, return target creature card with mana value 3 or less from your graveyard to the battlefield.
Menagerie — Whenever you attack, if there are five or more creature types among creatures you control, put a +1/+1 counter on target attacking creature and untap it.

Each artifact you control has all the activated abilities of other artifacts you control.

Exile the top five cards of your library. Until end of turn, you may play any number of cards exiled this way with mana value less than or equal to the number of colors among permanents you controlled as you cast United Fervor.

Enchant creature
As long as it's your turn, enchanted creature has indestructible.
Whenever enchanted creature attacks, it deals damage equal to its toughness to any target.

Create X 1/1 white Nymph creature tokens. Until end of turn, creatures you control gain protection from each color among permanents you controlled as you cast United Force.

Lifelink
Augmented — Whenever you cast a spell, if you've spent {W}{U}{B}{R}{G} to cast spells this turn, put a +1/+1 counter on United Guardian. It loses this ability and gains “Whenever United Guardian attacks, create two 1/1 blue Elemental creature tokens with flying that are tapped and attacking.”

Until end of turn, you can't lose the game, your opponents can't win the game, and your life total can't change.

When Unity Spheres enters, create two 1/1 colorless Construct artifact creature tokens.
Tap two untapped creatures you control: Add two mana of any one color.

Target player loses 3 life.

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.

Gain control of target creature with power less than or equal to the number of different creature types among creatures you control.

Return target creature card from your graveyard to the battlefield, then search target opponent's library for a creature card and put that card onto the battlefield under your control. Then that player shuffles.

{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 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.

Gain control of target nonland permanent if you control a permanent with a greater mana value. Otherwise, destroy that permanent.

Choose one —
• Creatures you control become colorless Forest lands until end of turn. (They have “{T}: Add {G}” and lose all other types and abilities.)
• Lands you control become 2/2 green creatures in addition to their other types and gain haste until end of turn.

Add X mana in any combination of colors, where X is the amount of mana spent to cast Unravel Shattered Worlds.
Coalesce {7} (You may cast this from your graveyard for {7}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)

Choose one, then choose another for each card named Unraveling in your graveyard.
• Counter up to one target spell.
• Scry 2, then draw a card.
• Up to three target lands your opponents control don't untap during their controller's next untap step.
• Creatures your opponents control get -4/-0 until end of turn.

Choose one, then choose another for each card named Unrelenting in your graveyard.
• Creatures get -1/-1 until end of turn.
• Create a 2/2 blue Elemental creature token.
• Each opponent loses 3 life and you gain 3 life.
• Search your library for a card with mana value 4 or greater, reveal it, put it into your hand, then shuffle.

Trample, ward {1}
Whenever you gain life, put a +1/+1 counter on Unrelenting Noble.
{1}, Sacrifice a permanent: You gain 2 life.

This spell costs {2} less to cast if your starting deck contained at least forty cards more than the minimum deck size.
When Unrivaled Fireweaver enters, you may exile a red instant or sorcery card you own from outside the game. Until the end of your next turn, you may play that card.

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.

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.