msem-instigator

Flying, vigilance
When Tyriel, Angelic Artisan enters, you may search your library for an Equipment card, reveal it, put it into your hand, then shuffle.
Whenever Tyriel attacks, you may put an Equipment card from your hand onto the battlefield, then attach it to Tyriel.

Archive 4 (As this enters, shuffle the top four cards of your main library into a new face up library. Sacrifice this after the archived library is empty.)
Whenever you draw a card from the archived library, destroy all nonland permanents you don't control with the same mana value as the drawn card.

When Umbersteed dies, target creature an opponent controls gets -4/-4 until end of turn.
Foreshadow {5}{B}{B} (You may cast this spell for its foreshadow cost. If you do, also trigger its “dies” abilities when it enters.)

Whenever you copy an instant or sorcery spell, you may pay {1}{U}. If you do, draw a card.
Whenever you cast an instant or sorcery spell, you may pay {1}{R}. If you do, Unbound Researchers deals 2 damage to target player or planeswalker.

When Unburdening Priest enters, you may exile any number of creatures you control not named Unburdening Priest, then return those cards to the battlefield under your control.

Surveil 2, then draw three cards. (To surveil 2, look at the top two cards of your library, then put any number of them into your graveyard and the rest on top of your library in any order.)

When Uncovered Mine enters and at the beginning of your upkeep, return a random card from your graveyard to your hand.

Concord — As long as there are four or more card types among permanents you control, you may cast the first spell you cast each turn without paying its mana cost.

This spell costs {1} less to cast for each artifact you control. (This applies before Treasures are sacrificed for mana.)
When Underhanded Deal enters, draw three cards.
Whenever you cast a spell, you lose 1 life.

Whenever a player casts a non-Dwarf spell or plays a non-Mountain land, this creature deals 2 damage to that player.
{1}{R}, Discard this card: Search your library for a Dwarf or Mountain card, reveal it, put it into your hand, then shuffle.

Undine Coven gets +1/+1 for each other Merfolk you control.
Whenever you cast a noncreature spell, Undine Coven deals 1 damage to target player or planeswalker.

When Undying Watcher enters, germinate. (Put a +1/+1 counter on a creature or create a 1/1 green Saproling creature token.)
Sacrifice another creature: Undying Watcher gains indestructible until end of turn.

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.

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

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.

Target attacking creature fights another target attacking creature.

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

Vanishing 5 (This creature enters 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.

At the beginning of each combat, harmonize twice. (To harmonize, trigger up to one harmony of a permanent you control.)
Harmony — Target creature gets +1/+1 and your choice of flying, haste, or vigilance until end of turn.

Harness (You may tap a creature you control as you cast this spell. If you do, reduce this spell's mana cost by that creature's power.)
Exile target nonland permanent an opponent controls. If this spell was harnessed by a token, you gain 5 life.

Haste
When Urud Stingswoop enters, it gains flying until end of turn.

Assault {1}{R} (Whenever this attacks, if it has no +1/+1 counters on it, you may pay its assault cost to put a +1/+1 counter on it.)
When Urudi Warlord assaults, it gains first strike until end of turn.

Flash
Death knell — Put a +1/+1 counter on each creature you control. (As a creature you control dies, trigger one death knell of that creature or another permanent you control.)