msem-instigator

When Undying Watcher enters, germinate. (Put a +1/+1 counter on a creature or create a 1/1 green Saproling creature token.)
Sacrifice another creature: Undying Watcher gains indestructible until end of turn.

When Helicos Octopus enters, scry 1. If an opponent is cursed, scry 3 instead.

Destroy target artifact. Create two 1/1 colorless Servo artifact creature tokens.

As Wayward Wanderers enters, you may have it become X/X with ward {X} and “Other creatures you control have base power and toughness X/X.”
{1}{G}: Return Wayward Wanderers to its owner's hand.

Careless Violence deals 2 damage to each creature. If a creature dealt damage this way would die this turn, exile it instead.

Scavenger Holdout enters tapped.
When Scavenger Holdout enters, you may pay {3}. If you do, create two 1/1 green Scout creature tokens.
{T}: Add {C}.

When Twisted Predator dies, you draw a card and you lose 1 life.

Whenever High-Priestess Nebti attacks or blocks, create a 2/2 white Cat creature token.
{1}{R}{R}, Tap an untapped Cat creature you control: That creature fights target creature you don't control.

Battalion — Whenever Battleborn Brute and at least two other creatures attack, Battleborn Brute gets +2/+2 until end of turn. Untap it.

Prowess
Whenever you cast your first instant or sorcery spell from your hand during each of your turns, if it doesn't have compose, it gains compose. (Then if you cast this from your hand, exile it and create a Saga token with “r3—You may cast a copy of this card from exile without paying its mana cost.”)

Menace
Cat creatures you control have menace.
When Basat Priest enters, create a 2/2 white Cat creature token.

Exile target creature, then exile target creature card from a graveyard. An opponent chooses one of them. Put the chosen card onto the battlefield under your control.

When Verdant Curtain Naturalist enters, you gain 3 life.
{T}: Add one mana of any color.

When Enhance Armor enters, return an enchantment card from your graveyard to your hand.
Whenever you cast an enchantment spell, put a +1/+1 counter on a creature you control.

Flying
When Skyborne Strategist enters, amass Soldiers 1. (Put a +1/+1 counter 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 you cast an instant or sorcery spell, create a 1/1 red Alien creature token with “This creature can't block.”
{2}{R}, Sacrifice two Aliens: Copy target instant or sorcery spell you control. You may choose new targets for the copy.

When Campaign Recruiter enters, you may search your library for a creature card with first strike, double strike, flying, improve, lifelink, melee, or vigilance, reveal it, put it into your hand, then shuffle.

Bloodsand Gulch enters tapped unless you control another Desert.
{T}: Add {B} or {R}.

Equipped creature gets +1/+1 and has prowess.
Equip {2}

Create two 1/1 red and white Warrior creature tokens. Those tokens gain first strike until end of turn.

Exile the top three cards of your library. Until the end of your next turn, you may cast nonland cards exiled this way.
{3}{U}{R}: Return Reckless Experiment from your graveyard to the
battlefield tapped and transformed.

Whenever an artifact you control enters, Master of Munitions deals 1 damage to each opponent.

When Clawing Shaman enters from your graveyard, you may exile it. If you do, return all creature cards from your graveyard to the battlefield.
{4}{B}{B}{B}, Sacrifice a creature: Return Clawing Shaman from your graveyard to the battlefield. Activate only as a sorcery.

Equipped creature gets +1/+0 and can't be blocked.
Equip Actor creature {1}
Equip {3}

Legacy (You may play this side of this card only from your graveyard. Exile it if it would be put into a graveyard or not resolve.)
Target Warrior you control deals damage equal to its power to target creature an opponent controls.