msem-instigator

When Posthumous Informant dies, investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

When Prodigious Telemancer enters, you may draw a card, then discard a card.
Whenever you cast an instant or sorcery spell, you may aetherize target creature you control. (To aetherize, create a token that's a copy of it, then exile that token.)

Renown 1 (When this creature deals combat damage to a player, if it isn't renowned, put a +1/+1 counter on it and it becomes renowned.)
Rafter Stalker can't be blocked by creatures with greater power.

Hexproof
Paranoia {1}{U} (You may cast this spell for its paranoia cost when a permanent you control leaves the battlefield.)

Flying
{2}{U}: Switch target creature's power and toughness until end of turn.

When Rhudai Overseer enters, look at the top four cards of your library. You may reveal an artifact or enchantment card from among them and put it into your hand. Put the rest on the bottom of your library in any order.

Hexproof
Each creature you control with a card inscribed onto it has hexproof.

Flying
{U}: Ripclaw Drake gets +1/-1 until end of turn.

Whenever a Survivor you control enters, scry 1. (To scry 1, look at the top card of your library. You may put that card on the bottom of your library.)

When Saia's Protege enters, gain control of target artifact or enchantment for as long as you control Saia's Protege.

Flash
When Scholar of Reflections enters, you may switch target creature's power and toughness until end of turn.

When Scrivener of Sha'Iv enters, draw a card and adjudicate. (Create a white Aura enchantment token with enchant creature and “Sacrifice this token: Untap enchanted creature” attached to target creature.)

When Sheltered Diviner enters, each player mills three cards.

Shimmering Seadragon gets +1/+0 and can't be blocked as long as you control a legendary creature.

Mark (Whenever this creature attacks, mark target creature until end of turn.)
Marked creatures your opponents control lose all abilities.

{1}, {T}: Surveil 2.
{U}, {T}, Discard a card: Look at the top card of your library. If it's a nonland card, you may cast it. (You still pay its costs)

Whenever you cast a noncreature spell, Slyten Technician gets +1/+0 until end of turn, then scry 1.

Whenever a permanent you control leaves the battlefield, if it had counters on it, you may put those counters on Stage Magician.
At the beginning of your end step, you may move any number of counters from Stage Magician onto target permanent you control.

{T}: Look at the top two cards of your library, then put them back in any order.

At the beginning of each end step, if you've cast a noncreature spell this turn, put a +1/+1 counter on Streetwise Spellseeker. Then if its power is 5 or greater, create a 4/4 white Angel Soldier creature token with flying.

Whenever you create a token, Substack Runner gets +1/+0 and can't be blocked until end of turn.

You may have Sun Yun enter as a copy of any creature on the battlefield, except her name is Sun Yun, Master of Man, she's legendary in addition to her other types, and she has “{2}{U}: Exile Sun Yun, then return her to the battlefield under her owner's control.”

If a creature entering the battlefield under your control causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.
{1}{U}, {T}: Exile another target creature. Return it to the battlefield under its owner's control at the beginning of the next end step.