msem-instigator

Amass Soldiers X, where X is the number of counters on permanents you control. (Put X +1/+1 counters on an Army you control. It's also a Soldier. If you don't control one, create an 0/0 black Soldier Army creature token first.)

Whenever Shoreline Stormers deals damage to a player, draw a card.
{2}{U}: Target creature can't be blocked this turn.

{T}: Add {C}.
{7}, {T}: Copy target instant or sorcery spell with {X} in its mana cost. You may choose new targets for the copy. This ability costs {1} less to activate for each instant and sorcery card in your graveyard.

Flash
When Keeper of Codices enters, you may exile target artifact or enchantment you control. If you do, return that card to the battlefield under its owner's control at the beginning of the next end step.

Lifelink
{1}{B}, Sacrifice Bloodbond Ritualist: Look at the top three cards of your library. Put one of them into your hand and the rest into your graveyard.

Flying
Whenever Naiala's Guide deals combat damage to a player, draw a card, then discard a card.

When Harvest Blighter enters, create a black Aura Curse enchantment token named Rotting Away attached to target player. The token has enchant player and “Whenever a creature enters under enchanted player's control, if it has toughness 2 or greater, put a -1/-1 counter on that creature.”

Draw a card. Scry 2.
Orchestrate {U} (You may exile this card from your hand anytime you could cast a sorcery for its orchestrate cost. When you next resolve a spell, you may cast this from exile without paying its mana cost.)

This spell costs {1} less to cast for each creature that died this turn.
At the beginning of your upkeep, put target creature card from a graveyard onto the battlefield under your control.
{1}, Sacrifice another creature: Zarad, the Final Adversary gains indestructible until end of turn.

Determined Chevalier has vigilance as long as it's embattled. (A creature is embattled if it has a counter on it or a permanent you control attached to it.)

Harness (You may tap a creature you control as you cast this spell. If you do, reduce this spell's mana cost by that creature's power.)
Target creature gets -X/-X until end of turn.

When Woopip Elder enters, germinate. (Put a +1/+1 counter on a creature or create a 1/1 green Saproling creature token.)

Exile the top card of your library. Impulsive Action deals damage to any target equal to that card's mana value plus one. Until end of turn, you may play that card.

As long as you control three or more artifacts, Treasury Master gets +2/+0 and has slipstream. (This creature can't be blocked as long as only creatures with slipstream are attacking.)

{G}: Exile target card from a graveyard. If it was a land card, put a +1/+1 counter on Sacrificial Bull.
{G}, Sacrifice Sacrificial Bull: You gain life equal to its power.

Experience (Whenever this creature attacks, if it has fewer than three +1/+1 counters on it, put a +1/+1 counter on it.)
Remove a +1/+1 counter from Kor Skyknight: It gains flying until end of turn.

When Mouthpiece of Yhzag enters, you may have target opponent create a tapped 1/1 colorless Human creature token.
Whenever Mouthpiece of Yhzag attacks, gain control of target Human creature you don't control with mana value 3 or less until end of turn. Tap it. It's attacking.

Defender
When Friend of Tides enters, rouse 2. (Distribute two +1/+1 counters among permanents you control. If they aren't creatures, tap them and they become 0/0 creatures in addition to their other types.)

Enchant creature you control
Enchanted creature gets +1/+1 and has hexproof and “{T}: Target player mills two cards.”
Whenever you play a land, untap enchanted creature.

({T}: Add {G} or {W}.)
As Sunlit Plaza enters, you may pay {1}. If you don't, Sunlit Plaza enters tapped.

Any number of target creatures you control each have base power and toughness 3/3 and become Beasts in addition to their other types until end of turn.
Reconstruct {2}{G}{G} (You may cast this from your graveyard for its reconstruct cost reduced by the mana value of a permanent you sacrifice as you cast it this way. Then exile this.)

Whenever you cast an instant or sorcery spell from your hand, put that card onto the battlefield face down as a 2/2 creature instead of putting it into your graveyard as it resolves.
Whenever a face-down creature you control deals combat damage to an opponent, you may exile it. If you do, you may cast it without paying its mana cost.

Destroy target creature or planeswalker. That permanent's controller loses 3 life unless that player sacrifices a nonland permanent or discards a card.

Revive {3}{G} ({3}{G}, Exile this card from your graveyard: Create a token that's a copy of it except it has no mana cost. Revive only as a sorcery.)

Whenever you cast a legendary spell, create a 1/1 white Human creature token.
{W}{U}{B}{R}{G}: Search your library for a legendary card, reveal it, put it into your hand, then shuffle. The next legendary spell you cast this turn costs {W}{U}{B}{R}{G} less to cast.