msem-instigator

Scry X. (Then exile this card. You may cast the creature later from exile.)

Concord — When Dolphin Rider enters, if there are four or more card types among permanents you control, you gain 5 life.

Pressure {3}{U}{B} (You may cast this spell for its pressure cost if seven or more cards are in your graveyard.)
Destroy up to one target creature. Return all other nonland permanents to their owners' hands.

Pressure {3}{U} (You may cast this spell for its pressure cost if seven or more cards are in your graveyard.)
Return target creature to its owner's hand. If this spell was cast for its pressure cost, put that creature into its owner's library second from the top instead.

Pressure {G} (You may cast this spell for its pressure cost if seven or more cards are in your graveyard.)
Return target card from your graveyard to your hand. Exile Drawn to the Light.

Double strike, trample, indestructible, haste
When Dredgeline Colossus enters, salvage up to eight noncreature, nonland cards. (You may exile them 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.)

Creatures you control get +1/+1 until end of turn. Merfolk you control get an additional +1/+1 until end of turn.

When Dualglaive Acolyte enters, create a green Aura enchantment token named Calamighty attached to target creature. The token has enchant creature and “Enchanted creature gets +1/+1 and can't be blocked by creatures with power 2 or less.”

When Duchess Odelia VII enters, search your library for a nonland permanent card with mana value 1 or less, reveal it, put it into your hand, then shuffle.

Untapped creatures you control get +1/+1.
Soldiers you control have vigilance.

Vigilance
Whenever an opponent casts a spell, create a Treasure token unless that player pays {1}, then create a 1/1 white Merfolk creature token unless that player pays {1}.
{W}{U}{B}{R}{G}, {T}: Other creatures you control get +3/+3 and gain vigilance and indestructible until end of turn.

{3}{R}: Target creature can't be blocked this turn if it's an artifact creature or has power 2 or less.

{T}, Sacrifice an artifact or creature: Each opponent loses 1 life and you gain 1 life.

Each other nontoken Elf and/or Warrior you control enters with an additional +1/+1 counter on it.
{G}{G}, {T}, Remove two +1/+1 counters from among creatures you control: Create two 1/1 green Elf Warrior creature tokens.

When Edina's Soulsinger enters, create a 1/1 blue Jellyfish enchantment creature token with slipstream. (It can't be blocked as long as only creatures with slipstream are attacking.)

Whenever you cast an artifact or enchantment spell, scry 1, then create a 1/1 white Merfolk creature token.
Whenever you cast a Merfolk spell, look at the top card of your library. If it's an artifact or enchantment card, you may reveal it and put it into your hand.

During each of your turns, you may cast a card with a cycling ability from your graveyard by discarding a card in addition to paying its other costs. If that spell would be put into your graveyard, exile it instead.
Cycling {2} ({2}, Discard this card: Draw a card.)

Scry 2. (Then exile this card. You may cast the creature later from exile.)

Choose one —
• Create two 1/1 blue Tentacle creature tokens.
• Untap target creature. It gets +2/+4 until end of turn.

Counter target creature spell. You may cast a copy of that spell. (You still pay its costs. The copy becomes a token.)

{T}: Add {C}.
Concord — {T}: Create a Treasure token. Activate only if there are four or more card types among permanents you control.

Copy target instant or sorcery spell. You may choose new targets for the copy.

At the beginning of your upkeep, return up to one target creature card from your graveyard to the battlefield. If that creature is a Cleric, you gain life equal to that creature's mana value. Otherwise, each player loses that much life.

When Enigma Mystic enters, mill three cards.
Enigma Mystic gets +2/+0 as long as there's a Shaman card in your graveyard.
{T}: Add one mana of any color. Activate only if you control another Shaman.

Enchant creature
You control enchanted creature.
Enchanted creature gets +1/+1 and has slipstream. (This creature can't be blocked as long as only creatures with slipstream are attacking.)