msem-instigator

Whenever Neon Claw Knight enters or attacks, choose one. Create a Function token with that effect. (It's an enchantment. As you cast an instant or sorcery spell, sacrifice any number of Functions to add their effects to that spell.)
• This spell can't be countered.
• This spell costs {R} less to cast.
• If this spell would deal damage to a permanent or player, it deals that much damage plus 1 instead.

Pressure—{B}, Pay 5 life. (You may cast this spell for its pressure cost if seven or more cards are in your graveyard.)
Create an X/X black Horror creature token, where X is the number of cards in your graveyard.

Once each turn, when another creature dies, you may crystallize. (Put a +1/+1 counter on a creature you control or create a Treasure.)
Whenever an artifact you control dies, Nihilistic Shock Trooper deals 1 damage to each opponent.

First strike
Crew 1 (Tap any number of creatures you control with total power 1 or greater: This Vehicle becomes an artifact creature until end of turn.)

Slipstream (This creature can't be blocked as long as only creatures with slipstream are attacking.)
Whenever you cast an enchantment, instant, or sorcery spell, Noble Barracuda gets +1/+0 until end of turn. Scry 1.

Enchant creature
Enchanted creature gets +3/+3.
Whenever enchanted creature attacks, you may put a creature card with mana value 2 or less from your hand or graveyard onto the battlefield tapped and attacking.

When North Ward Settler enters, choose one —
• Create a 1/1 white Dwarf creature token.
• Put a +1/+1 counter on North Ward Settler.

Enchant player
At the beginning of enchanted player's end step, gain control of a permanent they control.

Reach
When Oaken Sentry enters, you gain 1 life for each creature card in your graveyard.

Obscoriate deals 4 damage to target creature or planeswalker. The next time that permanent would die this turn, instead put a basalt counter on it, it becomes a Mountain land named Charred Remains, loses all other card types, and gains “At the beginning of your upkeep, Charred Remains deals 1 damage to you.” (It has “{T}: Add {R}” and loses abilities it already had.)

This spell costs {1} less to cast for each artifact and/or enchantment you control.
Trample
{1}, Sacrifice another cryptic permanent you control or exile a cryptic card from your graveyard: Put a +1/+1 counter on Observer of Aeons. (Artifacts, enchantments, and modal spells are cryptic.)

Whenever you attack, you may double target attacking creature's power. If you do, sacrifice it at the beginning of the next step.
Whenever one or more red creatures you control enter, creatures you control get +1/+0 and gain trample until end of turn.

Slipstream (This creature can't be blocked as long as only creatures with slipstream are attacking.)
{T}: Salvage a creature card. (Exile one from your graveyard until this creature leaves the battlefield. Whenever this creature deals combat damage to a player, put a card it salvaged into your hand.)

Slipstream (This creature can't be blocked as long as only creatures with slipstream are attacking.)
Concord — Once each turn, when an opponent casts a spell or activates an ability that targets a Merfolk or enchantment you control, you may counter that spell or ability if there are four or more card types among permanents you control.

Other Merfolk you control get +1/+1.
When Olantin Pearlreader enters, scry 2. Then draw a card if you control two or more other Merfolk.

When Old Salt enters, forebode. (Create a tapped colorless Omen artifact token with “{T}, Discard a card, Sacrifice this artifact: Draw a card.”)

When Olten Surveyor enters, choose any number. Each opponent creates a 1/1 colorless Servo artifact creature token for each mode chosen.
• Destroy target artifact or enchantment with mana value 3 or less.
• Shuffle up to four cards from target player's graveyard into their library.
• You gain 4 life.

Equipped creature gets +0/+3 and has menace. (It can't be blocked except by two or more creatures.)
Equip {1}

Whenever you draw a card, put a foreshadow counter on Ominous Seas.
Remove eight foreshadow counters from Ominous Seas: Create an 8/8 blue Kraken creature token.
Cycling {2} ({2}, Discard this card: Draw a card.)

Archive 6 (As this enters, shuffle the top six cards of your main library into a new face up library. Sacrifice this after the archived library is empty.)
Whenever a creature or planeswalker you control dies, you may play a card from the archived library. (You still pay its costs.)

Flying
At the beginning of your end step, up to one other target creature you control voyages. (If it isn't blocking or targeted by another spell or ability, it phases out.)
Whenever a creature you control phases in, you may have it become a copy of target creature you control until end of turn.

Trample
Orodu, the Onyx Wave can't block.
Whenever Orodu attacks, defending player may sacrifice a creature. If they do, prevent all combat damage Orodu would deal this turn.

Pressure {3}{B} (You may cast this spell for its pressure cost if seven or more cards are in your graveyard.)
When Oryxyth's Brood enters, you draw two cards and you lose 2 life.

Pressure—{4}{U}{B}, Sacrifice two creatures. (You may cast this spell for its pressure cost if seven or more cards are in your graveyard.)
Whenever Oryxyth enters or attacks, create an X/X black Horror creature token, where X is the number of cards in your graveyard.
{U}{B}, Sacrifice another creature: Gain control of target creature with power less than the sacrificed creature's power.

When Osseous Augur enters, target creature an opponent controls gets -1/-1 until end of turn. If that creature's controller is cursed, that creature gets -3/-3 until end of turn instead.