msem-instigator

Put a +1/+1 counter on target creature you control. Then that creature fights target creature you don't control. (Each deals damage equal to its power to the other.)

Creatures your opponents control get -4/-0 until end of turn. Scry 1. (To scry 1, look at the top card of your library. You may put that card on the bottom of your library.)

As an additional cost to cast this spell, discard a card.
Return target card from your graveyard to your hand.

Flying, deathtouch
{2}{B}{B}, Exile Weku, Malignity Spirit from your graveyard with four pact counters on him: You draw four cards and you gain 4 life.
At the beginning of your upkeep, if Weku is exiled with a pact counter on him, remove a pact counter from him. Then if Weku has no pact counters on him, you lose the game.

Equipped creature gets +3/+2 and must be blocked by a creature that doesn't share a color with it if able.
Equip {4}

Whenever a nontoken creature enters under your control, create a Field land token with “{T}, Sacrifice this land: Add one mana of any color.”
Whenever a nontoken land enters under your control, create a 1/1 white Peasant creature token.

Exile target creature, then return it to the battlefield under your control. Then sacrifice it.

Exile the top two cards of your library. You may play one of them until the end of your next turn.
Motley — If there are five or more names among nonland permanents you control, you may play both of them until the end of your next turn instead.

Settle the Dust deals 4 damage to each tapped creature.

{3}{B}: Regenerate Flesh Hoarder Ghoul. (The next time this creature would be destroyed this turn, it isn't. Instead tap it, remove all damage from it, and remove it from combat.)

Each other creature you control that's a Merfolk or an Elemental gets +1/+1.
Whenever you cast an instant, sorcery, or Merfolk spell, you may pay {1}. If you do, create a 1/0 blue Elemental creature token.

Gain control of target creature until end of turn. Untap that creature. Then create two 1/1 red Satyr creature tokens with “This creature can't block.” Creatures you control gain haste until end of turn.

Whenever Wild Dogs of the Night or another Horror you control enters, exile up to one target card in a graveyard. If that card was a creature card, you gain 2 life and put two +1/+1 counters on that Horror.

Draw three cards.
Lifecycle {3} ({3}, Discard this card: Create two tapped 1/1 colorless Elemental creature tokens.)

Substack Ports enters tapped.
{T}: Add {U} or {B}.
{U}{B}, {T}, Sacrifice Substack Ports: Conjure a card named Data-Point into your hand. (It's a sorcery that costs {2} with “Draw a card.”)

Target creature gains indestructible until end of turn.

Reach, deathtouch

{U}: Primordial Manifestation gets +1/-1 until end of turn.
Whenever Primordial Manifestation deals combat damage to a player, draw a card.

{T}: Add {C}.
{T}: Add {C}{C}. Spend this mana only to cast artifact spells. Activate only if you control three or more artifacts.

Enchant creature
Enchanted creature blocks each combat if able.
Whenever enchanted creature attacks, it loses flying until end of turn.

Target creature gets +1/+0 until end of turn and can't be blocked this turn.
Flashback {1}{U/B} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

{T}: Add {G} or {U}.
{T}, Sacrifice Sigil of Creation: Add {G}{U}.

Fleshcrawler gets +1/+0 for each player that has lost life this turn.

As Vaertris' Master Plan enters, exile the top five cards of any player's library.
You may play cards exiled with Vaertris' Master Plan.
When there are no cards exiled with Vaertris' Master Plan, return it to its owner's hand.

{W}{U}, {T}: Target creature gets +2/+2 and gains flying until end of turn.
{U}{B}, {T}: Target player mills three cards.
{B}{R}, {T}: Monolith of Ages deals 3 damage to any target.
{R}{G}, {T}: Target creature gets +4/+2 and gains trample until end of turn.
{G}{W}, {T}: Populate. (Create a token that's a copy of a creature token you control.)