msem-instigator

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 Strict Instructor attacks, harmonize. (Trigger up to one harmony of a permanent you control.)
Harmony — Tap or untap another target permanent.

Whenever you cast a spell, if it isn't your main phase, scry 1.

Flying
Whenever you cast a noncreature spell, note its mana value.
When Strix of Dark Omens dies, draw a card and create a 1/1 blue Bird creature token with flying for each different number noted with it.

When Student of Secrets enters, fateseal 1. (Look at the top one cards of an opponent's library, then put any number on the bottom and the rest on top in any order.)

Whenever Student of Winds attacks, upgrade target attacking creature. (Give it one of the listed counters it doesn't already have.)
• +1/+1
• Flying

Whenever Student of the Coil attacks, target creature gains poisonous 1 until end of turn. (Whenever that creature deals combat damage to a player, that player gets a poison counter.)

{T}: Target creature you control gets +1/+1 until end of turn. Activate only as a sorcery.
Scavenge {W} ({W}, Exile this card from your graveyard: Put a number of +1/+1 counters equal to this card's power on target creature. Scavenge only as a sorcery.)

When Student of the Scroll enters, scry 2.

At the beginning of combat on your turn, if you control six or more lands, put a +1/+1 counter on target creature you control.

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

When Suburban Farmer enters, you may search your library for a basic Plains card, reveal it, put it into your hand, then shuffle.
When Suburban Farmer dies, you gain 3 life.

Pay 2 life, Sacrifice a Clue: Draw a card.

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.

Sun-Dappled Paragon enters with a +1/+1 counter on it for each other creature you control.
Whenever another creature you control enters, put a +1/+1 counter on Sun-Dappled Paragon.

Deathtouch
At the beginning of your end step, if you control no Sharks, create a 1/1 blue and black Demon Shark creature token with “This creature can't block” and “When this creature deals combat damage to a player, sacrifice it. If you do, draw a card.”

Hexproof
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.)
As long as Sunrise Sentinel is renowned, other Scouts you control have hexproof.

Sunset Cliffs Hunter gets +1/+0 and has first strike as long as a player controls a permanent with a bounty counter on it.

Flying (This creature can't be blocked except by creatures with flying or reach.)

Sunwing has flying as long as it's your turn.

Each creature with a law counter on it can't attack or block.
{2}{W}, {T}: Remove all law counters from all permanents, then put a law counter on target creature.

Prowess
When Surviving Scavengers enters, you may draw a card, then discard a card.

Flying
At the beginning of your upkeep, you may pay {1}. If you do, put a +1/+1 counter on Swarm of the Dispossessed.
Sacrifice Swarm of the Dispossessed: Counter target spell with mana value X, where X is the number of +1/+1 counters on Swarm of the Dispossessed.

Flying
When Sweeper Drone enters, create a Function token with “Put a +1/+1 counter on each creature named Sweeper Drone you control.” (It's an enchantment. As you cast an instant or sorcery spell, sacrifice any number of Functions to add their effects to that spell.)