msem-instigator

Whenever Gentry Infiltrator deals combat damage to a player, you may search that player's library for a creature card and exile it. If you do, that player shuffles.
{2}{U}{U}: Gentry Infiltrator becomes a copy of a creature card exiled with it until end of turn.

Gifted Arcanomancer gets +1/+1 as long as you control a Mountain.
{3}{R}: Exile the top card of your library. Until end of turn, you may play that card.

Flying, prowess
{T}: Until end of turn, target land is every basic land type in addition to its other types.

This creature enters with a flying counter on it.
{2}{U}, Remove a counter from this creature: Search your library for a creature card with flying, reveal it, put it into your hand, then shuffle.

Prowess
Grizzled Stoker can't be blocked as long as you control an artifact.

Spirited (When this creature enters, you may activate one of its activated abilities without paying its cost.)
{U}, {T}: You may tap or untap target Human.

{U}, Give yourself a lore counter: Scry 1. This ability costs {2} more to activate for each lore counter you have.
{6}{U}, Remove three lore counters from yourself, Sacrifice Harbinger of Giradrus: Draw seven cards, then create two 4/4 red Dragon creature tokens with flying.

Flying
When Horned Spy enters, look at target player's hand.

Flying (This creature can't be blocked except by creatures with flying or reach.)
When Iridescent Familiar enters, if you control another creature with flying, draw a card.

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Spells you cast during combat cost {1} less to cast.

Flying
Morph {3}{B}{G} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)
When Ishim of Genesis is turned face up, put a +1/+1 counter on it, then return target instant or sorcery card from your graveyard to your hand.

Prowess
Whenever Knight-Academic attacks, scry 1.

{T}: Target land you control becomes the basic land type of your choice until end of turn.
At the beginning of each end step, if you spent three or more colors of mana to cast spells this turn, surveil 1.

{T}: Add {U}. Spend this mana only to activate an ability or cast an instant or sorcery spell.

Prowess
When Maktali Visionary enters, investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

{T}: Draw a card, then discard a card. If you discarded an instant, sorcery, Pirate, or Rogue card this way, create a 1/1 blue Tentacle creature token with “This creature can't block.”

Flying
When Messenger of the Heavens enters, surveil 1.
Whenever Messenger of the Heavens deals combat damage to a player, exile any number of target creatures in its pack, then return them to the battlefield under your control. (Two or more creatures you control with equal power are in a pack.)

Flying
{1}{U}: Reveal the top card of your library. Moonwing Watcher's base power becomes equal to that card's mana value.
Prophecy {U} (Once each turn, you may exile a card with prophecy as you reveal it. When you do, you may cast it for its prophecy cost as long as it's exiled.)

Whenever Netsight Trickster deals combat damage to an opponent, create a Function token with “Draw a card. Then discard a card unless you pay {2}.” (It's an enchantment. As you cast an instant or sorcery spell, sacrifice any number of Functions to add their effects to that spell.)

Whenever Nightrail Printer attacks, you may tap target creature.

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
At the beginning of your end step, if you've cast three or more spells this turn and Nizev Enforcer isn't a token, create a token that's a copy of it.

Flying
Menagerie — When Northrime Messenger enters, if there are five or more creature types among creatures you control, you may search your library for a Quest card, reveal it, put it into your hand, then shuffle.

Prowess
Whenever Outsider Alchemist deals combat damage to a player, create a Vial token. (It's an artifact with “{1}, Sacrifice this and another permanent: Draw a card. Activate only during your turn.”)

Whenever you cast an instant spell during your main phase, copy that spell. You may choose new targets for the copies.

{U}, {T}: Sacrifice any number of nontoken creatures. Create an X/X blue Horror creature token, where X is the total power of those creatures. Then if X is 4 or greater, you may transform Performer of Brilliance.