msem-instigator

When Uncovered Secrets enters, search your library for an artifact card, reveal that card, then shuffle and put that card on top.
Concord — Creatures you control get +1/+1 as long as there are four or more card types among permanents you control.

When Undead Necromancer enters, search your library for a card, put that card into your graveyard, then shuffle.
As long as this card is in your graveyard, its name is Undead Servant.

At the beginning of each opponent's upkeep, that player may discard their hand. If the player does, sacrifice Under the Gun. Otherwise, put a bullet counter on Under the Gun, then that player loses life equal to the number of bullet counters on it.

Bleed {1}{B} (You may cast this spell for its bleed cost if an opponent lost life this turn.)
When Undermurk Scavenger enters, you draw a card and you lose 1 life.

As an additional cost to cast this spell, exile a creature card from your graveyard.
You draw three cards and you lose 3 life.

Archive 0 (As this enters, shuffle the top zero cards of your main library into a new face up library. Sacrifice this after the archived library is empty.)
As Undue's Study enters, shuffle your graveyard into the archived library.

Return up to two target creature cards with total mana value 4 or less from your graveyard to the battlefield.

Zombiecycling {1}{B} ({1}{B}, Discard this card: Search your library for a Zombie card, reveal it, and put it into your hand, then shuffle.)
Unearth {1}{B} ({1}{B}: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the end step or if it would leave the battlefield. Unearth only as a sorcery.)

Unearthed Legion's power and toughness are each equal to the number of cards in your graveyard.
At the beginning of your upkeep, mill a card.

Whenever a creature you control dies, you may return all cards that were inscribed onto that creature and all Auras that were attached to that creature to their owners' hands.

Enchant creature you control
Enchanted creature gets +1/+1.
When enchanted creature dies, return it to the battlefield under your control, then arm it. (Create a colorless Equipment artifact token with “Equipped creature gets +1/+0” and equip {2}, then attach it to that creature.)

Search your library for a card, reveal it, then shuffle and put that card on top of it. If you revealed a noncreature card this way, each opponent loses 2 life and you gain 2 life.

Menace
{3}{B}, Discard a card: Unhallowed Singers gets +3/+0 until end of turn. Whenever it deals combat damage to a player this turn, they discard a card.

{T}: Add one mana of any color.
{T}, Sacrifice Unicorn of the Vale: Add three mana of any one color.

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.

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 United in Battle enters, look at the top six cards of your library. You may reveal a Dwarf or Elf card from among them and put it into your hand. Put the rest on the bottom in a random order.
Whenever a Dwarf or Elf you control enters, put a +1/+1 counter on it.

{6}{W}: Tap all creatures target player controls.

Whenever a creature dies, you may put a progress counter on Unorthodox Methods.
[progress 2-6] Whenever you cast a noncreature spell, Unorthodox Methods deals 2 damage to any target and you gain 2 life.
[progress 7+] Whenever you cast a noncreature spell, Unorthodox Methods deals 4 damage to any target and you gain 4 life.
Whenever you cast a noncreature spell, CARDNAME deals 4 damage to any target and you gain 4 life.

At the beginning of your upkeep, each player mills two cards, then reveals the top card of their library and puts it on the bottom of their library.

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.

Haste
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Whenever Unruly Magus deals combat damage to a player, draw a card.