msem-instigator

Rhapsody {4}{R}{R} (Pay {4}{R}{R} to cast this as a 4/4, or as a sorcery to make it become a 4/4.)
Double strike

Choose one —
• When you next cast an instant or sorcery spell this turn, copy that spell. You may choose new targets for the copy.
• Target creature you control gains double strike until end of turn

{1}, Sacrifice another creature: Crystallize. Activate only as a sorcery. (Put a +1/+1 counter on a creature you control or create a Treasure.)
{W}{U}{B}{R}{G}: Target creature gets +3/+3 and gains trample until end of turn. Activate only as a sorcery.

Rhapsody {3}{R}{R} (Pay {3}{R}{R} to cast this as a 4/4, or as a sorcery to make it become a 4/4.)
Whenever Vindictive Guardian or another creature you control enters, if that creature's power is 4 or greater, create a Treasure token.

Crystallize. (Put a +1/+1 counter on a creature you control or create a Treasure.)
Voice of the Universe deals 2 damage to each creature.

When Voltaic Conduit enters, it deals 5 damage to target creature or planeswalker you don't control.
Whenever you attack, you may discard a card. If you do, draw a card.

WZ-18 Troublemaker enters with a +1/+1 counter on it.
When WZ-18 Troublemaker dies, put its counters on target creature you control.
{1}{R}, Exile WZ-18 Troublemaker from your graveyard: It deals 2 damage to each opponent.

Trample
Whenever another Horror you control enters, put a +1/+1 counter on Abominable Xenoflora.

Search your library for a basic land card, put it onto the battlefield, then shuffle.
Crystallize. (Put a +1/+1 counter on a creature you control or create a Treasure.)

Whenever Ancient Durumderm attacks, you may return another creature you control to its owner's hand. If you do, create a Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)

When AOSE Extractor enters, crystallize. (Put a +1/+1 counter on a creature you control or create a Treasure.)

Vigilance, trample
Whenever another Horror you control enters, choose one —
• Destroy target artifact or enchantment.
• You gain 4 life.
• Apex Abomination fights another target creature.

Haste
Augmented — When Attuned Lifeform enters, if you've spent {W}{U}{B}{R}{G} to cast spells this turn, put a +1/+1 counter on each creature you control. They gain vigilance until end of turn.

{T}: Add one mana of any color a basic land you control could produce.

When Bioluminescent Predator dies, draw a card, then you may put a land card from your hand onto the battlefield.

When Brand New Species enters, create a tapped 3/2 green Horror creature token.
Augmented — At the beginning of each end step, if you've spent {W}{U}{B}{R}{G} to cast spells this turn, put a +1/+1 counter on up to one target Horror you control.

Create a 3/2 green Horror creature token.
Reconstruct {4}{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.)

Target creature gets +3/+3 and gains trample until end of turn.
Reconstruct {3}{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.)

Vigilance, reach
When DL-19 Reject enters, target creature you control gets +2/+2 until end of turn.

Creatures you control enter with a +1/+1 counter on them if you spend three or more colors of mana to cast them.

Return up to six target cards in your graveyard that don't share colors to your hand.
Exile Earthly Ambitions.

Vigilance
{G}, {T}: Exile up to three target cards from graveyards. If two or more of those cards share a card type, create a 1/1 colorless Servo artifact creature token.

Destroy target artifact or enchantment. Surveil 1. (Look at the top card of your library. You may put that card into your graveyard.)

Whenever Hurried Scavenger attacks or blocks, you may mill two cards.
Hurried Scavenger gets +4/+4 as long as you have five or more card types among cards in your graveyard.

Whenever Insatiable Abomination or another Horror you control enters, each player mills four cards.
Exile a creature card from your graveyard: Tap target Horror you control. It gains indestructible until end of turn.