msem-instigator

Enchant creature
Enchanted creature has first strike. (That creature deals combat damage before creatures without first strike.)

Archive 0 (As this enters the battlefield, 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 the battlefield, shuffle your graveyard into the archived library.

[+2]: Exile up to three target cards from graveyards.
[+1]: Create a 2/1 black Horse Zombie creature token with lifelink.
[0]: If Undue has six or more loyalty counters on him, each opponent returns a creature card of their choice from a graveyard to the battlefield under your control.

Creatures you control get +2/+0 and have deathtouch as long as ten or more cards are in your graveyard.

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.)

Enchant land
When Unexplored Regions enters the battlefield, draw a card.
Enchanted land is an artifact in addition to its other types and has “{T}: Add one mana of any color.”

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.

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.

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

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.

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.

As Unlikely Growth enters the battlefield, choose grow or maintain.
Whenever a land enters the battlefield under your control,
• Grow — Put a +1/+1 counter on target creature you control.
• Maintain — Target creature you control gains trample and indestructible until end of turn.

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.

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.

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.

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

Whenever a creature dies, you may pay 1 life. If you do, draw a card.

All creatures have “When this creature enters the battlefield, destroy target creature with a lesser mana value.”

Constructs you control have haste.
When Urak, Voice of the Horde or another Construct enters the battlefield under your control, creatures you control get +1/+0 until end of turn.
Respawn (When this creature dies, if it attacked this turn, return it to its owner's hand.)

If you would create a token, you may instead create a tapped 2/2 green Faerie Bard creature token.
Whenever one or more creature tokens you control deal combat damage to a player, that player sacrifices an artifact or enchantment.

When Urn of Heroes enters the battlefield, you may search your library for a legendary card, put that card into your graveyard, then shuffle.
{T}: Add {C}.

You may have Urushi, the Ripple in the Smoke enter the battlefield as a copy of any creature on the battlefield, except it's an enchantment. (It's not a creature.)