msem-instigator

Flying
Whenever an opponent discards a card, you may exile it. If you do, create a 1/1 black Bird creature token with flying and “This creature can't block.”
{B}, Sacrifice three Birds: You may cast a card exiled with Krahen, Dusk's Call without paying its mana cost.

When Hail to the Queen enters, each player sacrifices a creature.
Whenever a nontoken creature you control dies, you may pay its mana cost. If you do, create a token that's a copy of it.

Counter up to one target spell unless its controller pays {2}. Until end of turn, you may cast spells as though they had flash.

When Temur Falconer enters, create a 1/1 blue Bird creature token with flying.
Whenever a creature you control with flying deals combat damage to a player or planeswalker, put a +1/+1 counter on Temur Falconer.

Synchronous Battle Armor and equipped creature get +1/+1 for each artifact you control.
Whenever equipped creature attacks, tap up to three target creatures.
Reconfigure {3}{U}{U} ({3}{U}{U}: Attach to target creature you control; or unattach from a creature. Reconfigure only as a sorcery. While attached, this isn't a creature.)

You may reveal the second card you draw each turn as you draw it. When you do, create a 2/2 blue Avatar Wizard creature token with prowess if it's a creature card. If it's a land card, create a Treasure token. If it's a noncreature, nonland card, Steward of Second Sphere can't be blocked this turn.
{3}{W/U}{W/U}: Scry 2.

This spell can't be countered.
Draw a card.
Reprise {2}{U} (As you cast an instant or sorcery spell, you may exile one card with reprise from your graveyard and pay its reprise cost. If you do, add its effects to that spell.)

When Rune-Scribe's Apprentice enters, target player mills four cards.

Scry 2, then draw a card.
If you control a legendary permanent, investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

Flash
When Qililia's Scavenger enters, look at the top six cards of your library. You may put a Merfolk card with lesser mana value from among them onto the battlefield. Put the rest on the bottom of your library in a random order.
Other Merfolk you control get +1/+1.

Defender (This creature can't attack.)
Whenever you cast a spell during an opponent's turn, scry 1. (To scry 1, look at the top card of your library. You may put that card on the bottom of your library.)

Draw two cards, then discard two cards. Then if you cast Price of Wisdom from your graveyard, create a 3/3 blue Sphinx creature token with flying.
Flashback {4}{U}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Prowess
Whenever you cast your first noncreature spell during each of your turns, create a 1/1 blue Reflection Wizard creature token with prowess.

Slipstream (This creature can't be blocked as long as only creatures with slipstream are attacking.)
Whenever Manipulator of Waves attacks, mill three cards. Then create a 0/0 blue Elemental Serpent creature token with “This creature gets +1/+1 for each five cards in your graveyard.”

Counter target spell unless its controller pays {1}. If you control a creature with flying, counter that spell unless its controller pays {4} instead.

At the beginning of your upkeep, each opponent mills cards equal to the number of card types among permanents you control.

Slipstream (This creature can't be blocked as long as only creatures with slipstream are attacking.)
When Dancer of the Great Current enters, tap up to one target creature. If you control two or more other creatures that are Merfolk, Wizards, or Rogues, instead return that creature to its owner's hand and put a +1/+1 counter on Dancer of the Great Current.

Create two 1/2 blue Bird creature tokens with flying.
Coalesce {5}{U}{U} (You may cast this from your graveyard for {5}{U}{U}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)

Whenever you attack, create a white Equipment artifact token with “Equipped creature gets +1/+1” and equip {1}. Attach it to an attacking creature you control.
At the beginning of your end step, untap each embattled creature you control. (A creature is embattled if it has a counter on it or has a permanent you control attached to it.)

Enchant creature
When Sprawled Arming enters, put a +1/+1 counter on enchanted creature.
Enchanted creature has first strike.
{5}: Return Sprawled Arming to its owner's hand.

Senaturian Legion gets +1/+1 for each other creature on the battlefield named Senaturian Legion.
A deck can have any number of cards named Senaturian Legion.

When you cast Senaturian Centurion, reveal cards from the top of your library until you reveal a creature card with mana value 2 or less. Copy that card, then put the revealed card into your hand. You may cast the copy without paying its mana cost. Put the revealed cards on the bottom of your library in a random order.

Enchant creature
Enchanted creature can't attack or block.
Foresee — As you draw Prophecy of Peace, you may reveal it and pay {W}. When you do, target creature can't attack or block this turn.

When Prized Holsteins enters, create a 2/2 white Dwarf creature token.
When Prized Holsteins leaves the battlefield, you gain 2 life.

Whenever you gain life, Militant Youth gets +1/+1 until end of turn.