msem-instigator

Purger of Blights enters with a -1/-1 counter on it.
{2}{B}{G}, {T}, Remove a -1/-1 counter from a creature you control: Draw a card.

Trample
Effigy of Harvest gets +1/+1 as long as your fealty to Forests is four or greater. (Each Forest you control counts towards your fealty to Forests.)

Take an extra turn after this one. During that extra turn, you may cast spells you own not named See the World from outside the game by tapping an untapped Scout you control in addition to paying their mana costs.
Exile See the World.

{1}, Sacrifice a creature: Ever-Hungry Tanbaly gains indestructible until end of turn. Tap it.

Trample
Whenever a creature attacks, Alpha Stag gets +2/+2 until end of turn.

When Shardsong Seedling enters, conjure two cards named Data-Point into your hand. (It's a sorcery that costs {2} with “Draw a card.”)

This spell costs {1} less to cast for each card in your graveyard.
Arise {9}{B}. This ability costs {1} less to activate for each other card in your graveyard. ({9}{B}, Exile this from your graveyard as a sorcery: Create a black token copy of it that's also a Zombie and can't block.)

Menace, lifelink
When Fallen Hero leaves your graveyard, if it wasn't exiled, you may return target creature card not named Fallen Hero from your graveyard to your hand.

If a nontoken creature you don't control would die, exile it instead.
Once each turn, you may cast a card exiled with Accursed Existence.

When Fang of Andazir enters, each player sacrifices a permanent.
Whenever you sacrifice a creature for the first time each turn, create a 1/1 red Dog creature token.

First strike
Sacrifice this creature: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

When Scion of Pestilence enters, create a black enchantment token named Blight with “At the beginning of your upkeep, you lose 1 life.”

Erratic (When this creature dies, reveal the top four cards of your library. Put a creature card that costs less than this revealed this way onto the battlefield and the rest on the bottom of your library in any order.)
Morph {1}{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 Keeper of Blue Incense enters, submerge target card from your graveyard. (To submerge a card, exile it, then put it on the battlefield face down under its owner's control as a 2/2 creature.)

First strike

First strike
When Hunted Haunt dies, create a 1/1 black Scout creature token.

Whenever you cast a cryptic spell, creatures you control get +1/+1 until end of turn. (Artifacts, enchantments, and modal spells are cryptic.)

Flying

{T}: Kanaan Wardriver deals 1 damage to target creature you control. That creature gains haste until end of turn.

You may have Raging Reflection enter as a copy of any creature on the battlefield, except it has “When this creature enters, it fights another target creature that shares a name with it.”

{T}, Pay 1 life: Add {R} or {G}.
{1}, {T}, Sacrifice Forgotten Shrine: Investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

Return up to two target creatures to their owners' hands.

Flying, haste
Volcano Tyrant enters with a first strike counter on it.
{2}{R}, Remove a first strike counter from Volcano Tyrant: Double its power and it gains trample until end of turn.

When Wild Festivities enters or at the beginning of your upkeep, you may put a creature card from your hand onto the battlefield. If you do, each opponent creates a 1/1 blue Frog creature token.

Whenever Brine Kelpie attacks, you may tap target creature an opponent controls.
Ride {2}{U} ({2}{U}: Transform this and attach it to target creature you control without a Steed. Ride only as a sorcery.)