Mist-Cloaked Herald

The Surgical Bay

The Surgical Bay enters tapped.
{T}: Add {U}.
{1}{U}, {T}, Sacrifice The Surgical Bay: Draw a card.

Growth Spiral

Draw a card. You may put a land card from your hand onto the battlefield.

River Sneak

River Sneak can't be blocked.
Whenever another Merfolk you control enters, River Sneak gets +1/+1 until end of turn.

Merfolk Skydiver

Flying
When Merfolk Skydiver enters, put a +1/+1 counter on target creature you control.
{3}{G}{U}: Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Herald of Secret Streams

Creatures you control with +1/+1 counters on them can't be blocked.

Keep Safe

Counter target spell that targets a permanent you control.
Draw a card.

Fading Hope

Return target creature to its owner's hand. If its mana value was 3 or less, scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Reconnaissance Mission

Whenever a creature you control deals combat damage to a player, you may draw a card.
Cycling {2} ({2}, Discard this card: Draw a card.)

Song of Freyalise

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I, II — Until your next turn, creatures you control gain "{T}: Add one mana of any color."
III — Put a +1/+1 counter on each creature you control. Those creatures gain vigilance, trample, and indestructible until end of turn.

Cartouche of Knowledge

Enchant creature you control
When Cartouche of Knowledge enters, draw a card.
Enchanted creature gets +1/+1 and has flying.

Forest

Temple of Mystery

This land enters tapped.
When this land enters, scry 1. (Look at the top card of your library. You may put that card on the bottom.)
{T}: Add {G} or {U}.

Merfolk Mistbinder

The Hunter Maze

The Hunter Maze enters tapped.
{T}: Add {G}.
{1}{G}, {T}, Sacrifice The Hunter Maze: Draw a card.

Gaea's Gift

Put a +1/+1 counter on target creature you control. It gains reach, trample, hexproof, and indestructible until end of turn. (It can't be the target of spells or abilities your opponents control. Damage and effects that say "destroy" don't destroy it.)

Island

Jade Bearer

When Jade Bearer enters, put a +1/+1 counter on another target Merfolk you control.

Evolving Wilds

{T}, Sacrifice this land: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Stasis Field

Enchant creature
Enchanted creature has base power and toughness 0/2, has defender, and loses all other abilities.

Triton Shorestalker

Fabled Passage

{T}, Sacrifice Fabled Passage: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle. Then if you control four or more lands, untap that land.

Jungleborn Pioneer

When Jungleborn Pioneer enters, create a 1/1 blue Merfolk creature token with hexproof. (It can't be the target of spells or abilities your opponents control.)

Broken Bond

Destroy target artifact or enchantment. You may put a land card from your hand onto the battlefield.