msem-instigator

Whenever Tide Crasher attacks, if you control another Merfolk, tap target creature defending player controls.

First strike, vigilance
When Subnautical Legionnaire enters, choose artifact, enchantment, or Merfolk. Exile target nonland permanent you don't control until you control no permanents of the chosen type.

When Seafloor Shrine enters and when you sacrifice it, create a 1/1 white Merfolk creature token.
{1}{W}, Sacrifice Seafloor Shrine: Draw a card.
Cycling {2} ({2}, Discard this card: Draw a card.)

Schoolmaster gets +1/+1 for each other Merfolk you control.
When Schoolmaster enters, create a 1/1 white Merfolk creature token.

Slipstream (This creature can't be blocked as long as only creatures with slipstream are attacking.)
As long as you control three or more artifacts, Regal Seasnake has vigilance. (Attacking doesn't cause it to tap.)

When Pensive Muse enters, create a white Aura enchantment token named Seal's Love attached to target creature you control. The token has enchant creature and “Enchanted creatures you control get +1/+1.”

Concord — When Palace Servant enters, if there are four or more card types among permanents you control, create two 1/1 white Merfolk creature tokens.

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.

Choose one —
• Return target artifact or enchantment card from your graveyard to your hand.
• Return target creature card with mana value 2 or less from your graveyard to your hand.
Cycling {2} ({2}, Discard this card: Draw a card.)

When Militant's Standard enters, draw a card if you control a Merfolk.
Equipped creature gets +2/+1.
Equip {2}

Whenever Merrow Legendmaker attacks, look at the top five cards of your library. You may reveal an Aura, Aurashaper, or Equipment card from among them and put it into your hand. Put the rest on the bottom of your library in any order.

Majestic Nauticorn has first strike as long as it's attacking.
Cycling {W} ({W}, Discard this card: Draw a card.)

When Lilyreed Triton enters, create a white Aura enchantment token named Triton's Gift attached to target creature. The token has enchant creature and “Enchanted creature gets +1/+0 and can't be blocked by creatures with power 3 or greater.”

Exile all creatures, then for each creature exiled this way, you may return it to the battlefield under its owner's control. For each creature you didn't return to the battlefield this way, its owner may search their library for a basic land card and put it onto the battlefield tapped. Each player that does shuffles.

Exile target creature if its controller controls more lands than you.
Cycling {2} ({2}, Discard this card: Draw a card.)

Concord — This spell costs {2} less to cast if there are four or more card types among permanents you control.
Vigilance (Attacking doesn't cause this creature to tap.)

Concord — At the beginning of your upkeep, if there are four or more card types among permanents you control, you gain 1 life and 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.)

Enchant creature
Enchanted creature gets +2/+2.
Concord — As long as there are four or more card types among permanents you control, enchanted creature has slipstream. (This creature can't be blocked as long as only creatures with slipstream are attacking.)

Vigilance
Whenever Glittering Narwhal is dealt damage, create a Treasure token. (It's an artifact with “{T}, Sacrifice this permanent: Add one mana of any color.”)

When Gilded Merrow enters, if an opponent controls more lands than you, create a Treasure token. (It's an artifact with “{T}, Sacrifice this permanent: Add one mana of any color.”)

Lifelink (Damage dealt by this creature also causes you to gain that much life.)
Slipstream (This creature can't be blocked as long as only creatures with slipstream are attacking.)

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.

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

When Dawson's Bouncer enters, choose one —
• Put a +1/+1 counter on Dawson's Bouncer.
• Create a Treasure token. (It's an artifact with “{T}, Sacrifice this artifact: Add one mana of any color.”)

Vigilance
When Coralight Sentinel enters, create a white Aura enchantment token named Crab's Resolve attached to target creature. The token has enchant creature and “Enchanted creature gets +0/+2.”