msem-instigator

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.

Create three 1/1 colorless Servo artifact creature tokens.
Exile Unending Armies. At the beginning of your upkeep, if you have more life than each opponent, you may cast it without paying its mana cost. Otherwise, put it into your graveyard.

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.)

Target creature you control explores. Then it fights up to one target creature you don't control. If that creature has flying, the creature you control deals damage equal to its power to it instead. (Reveal the top card of your library. Put it into your hand if it's a land. Otherwise, put a +1/+1 counter on that creature, then you may put that card in your graveyard.)

Flying
When Unfettered Atrocity enters the battlefield, destroy target creature or planeswalker.

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.

If you would lose life, exile that many cards from the top of your library instead.
If you would gain life, draw that many cards instead.
When Unhallowed Concordat leaves the battlefield, you lose life equal to the number of cards you own in exile.

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.

Whenever you cast an enchantment spell, reveal the top card of your library. If it's an enchantment card, you may put it onto the battlefield.

If you would draw a card, you may return an instant or sorcery card from your graveyard to your hand instead.
{U}: Draw three cards.

When Unite Against Evil enters the battlefield, 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.

Look at the top six cards of your library. Put up to two creature cards with mana value 3 or less from among them onto the battlefield. Put the rest on the bottom of your library in a random order. Then you gain 1 life for each Angel, Demon, Faerie, and/or Spirit you control.

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.

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.”

Cadence (Whenever you cast a spell, if its mana value is greater than this creature's power, put a +1/+1 counter on this creature.)
United Patrol can block an additional creature each combat.

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 the battlefield, 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 enters the battlefield under your control, put a +1/+1 counter on it.

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

Creatures you control have base power 4 and gain trample until end of turn.

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.