msem-instigator

Rhapsody {4}{R}{R} (Pay {4}{R}{R} to cast this as a 4/4, or as a sorcery to make it become a 4/4.)
Double strike

Rhapsody {4}{U}{U} (Pay {4}{U}{U} to cast this as a 4/4, or as a sorcery to make it become a 4/4.)
Whenever you cast a noncreature spell, Triumvirate Inductee gets +1/+1 until end of turn. Then if its power is 4 or greater, you may tap or untap target permanent.

Triumvirate Infiltrator has flying as long as you control another Elemental.

Rhapsody {4}{W}{W} (Pay {4}{W}{W} to cast this as a 4/4, or as a sorcery to make it become a 4/4.)
Triumvirate Strategist has first strike as long as it's attacking.

Choose one —
• When you next cast an instant or sorcery spell this turn, copy that spell. You may choose new targets for the copy.
• Target creature you control gains double strike until end of turn

Flash
Flying
When Turela, Defiant Angel enters, exile all other creatures you control. Return them to the battlefield under their owner's control at the beginning of the next end step.

Each player chooses three permanents they control, then returns the others to their owners' hands. Each player loses all unspent mana.
Exile Turn the Record Over.

When Twisted Predator dies, you draw a card and you lose 1 life.

{1}, Sacrifice another creature: Crystallize. Activate only as a sorcery. (Put a +1/+1 counter on a creature you control or create a Treasure.)
{W}{U}{B}{R}{G}: Target creature gets +3/+3 and gains trample until end of turn. Activate only as a sorcery.

Flash
When Twisted Speaker enters, return target spell to its owner's hand. That spell's controller loses 2 life.

Spirited (When this enters, you may activate one of its activated abilities without paying its cost.)
{5}, {T}, Discard a card: Create a 0/0 colorless Construct artifact creature token with “This creature gets +1/+1 for each artifact you control.” It can't block this turn.

Cast this spell only if you control a creature.
Exile all creatures.

Whenever a Wizard you control deals damage to a player, draw a card.

Whenever Uncanny Allocator enters or attacks, give any number of permanents and/or players with counters on them another counter of each kind already there.

Unceasing Flames deals X damage to any target, where X is 2 plus the number of cards named Unceasing Flames in your graveyard.
Conjure three cards named Unceasing Flames and shuffle them into your main library.

Look at the top two cards of your library. Put one of them into your hand, then you may have any number of players each mill three cards.

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.

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 land
When Unexplored Regions enters, 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 draw a card, you may return an instant or sorcery card from your graveyard to your hand instead.
{U}: Draw three cards.

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.

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.

Rhapsody {4}{U}{U} (Pay {4}{U}{U} to cast this as a 4/4, or as a sorcery to make it become a 4/4.)
When Unstable Prophet enters, surveil X, where X is its power. (Look at the top X cards of your library, then put any number of them into your graveyard and the rest on top of your library in any order.)