{1}{U}: Adapt 1. (If this creature has no +1/+1 counters on it, put a +1/+1 counter on it.)

Whenever one or more +1/+1 counters are put on Benthic Biomancer, draw a card, then discard a card.

Draw two cards. Then discard a card unless you attacked this turn.

{1}{G}, {T}: This turn, each creature you control enters the battlefield with an additional +1/+1 counter on it.

{1}{U}, {T}: Move a +1/+1 counter from target creature you control onto another target creature you control.

Whenever another Merfolk enters the battlefield under your control, put a +1/+1 counter on target Merfolk you control.

Counter target spell with mana value 4 or greater.

When Forerunner of the Heralds enters the battlefield, you may search your library for a Merfolk card, reveal it, then shuffle and put that card on top.

Whenever another Merfolk enters the battlefield under your control, put a +1/+1 counter on Forerunner of the Heralds.

Deathtouch

When God-Eternal Rhonas enters the battlefield, double the power of each other creature you control until end of turn. Those creatures gain vigilance until end of turn.

When God-Eternal Rhonas dies or is put into exile from the battlefield, you may put it into its owner's library third from the top.

Whenever a nontoken creature enters the battlefield under your control, if it doesn't have the same name as another creature you control or a creature card in your graveyard, draw a card.

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

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

When Jadelight Ranger enters the battlefield, it explores, then it explores again. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then put the card back or put it into your graveyard. Then repeat this process.)

Each creature you control with a +1/+1 counter on it has "{T}: Add one mana of any color."

-1: Put a +1/+1 counter on target creature.

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

Spells your opponents cast that target a Merfolk you control cost {2} more to cast.

Abilities your opponents activate that target a Merfolk you control cost {2} more to activate.

Kumena's Speaker gets +1/+1 as long as you control another Merfolk or an Island.

Tap another untapped Merfolk you control: Kumena, Tyrant of Orazca can't be blocked this turn.

Tap three untapped Merfolk you control: Draw a card.

Tap five untapped Merfolk you control: Put a +1/+1 counter on each Merfolk you control.

When Merfolk Branchwalker enters the battlefield, it explores. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then put the card back or put it into your graveyard.)

Other Merfolk you control get +1/+1.

Flying

When Merfolk Skydiver enters the battlefield, 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.)

Flash

When Merfolk Trickster enters the battlefield, tap target creature an opponent controls. It loses all abilities until end of turn.

Mist-Cloaked Herald can't be blocked.

Counter target noncreature spell.

River Sneak can't be blocked.

Whenever another Merfolk enters the battlefield under your control, River Sneak gets +1/+1 until end of turn.

Flying, trample

When Roalesk, Apex Hybrid enters the battlefield, put two +1/+1 counters on another target creature you control.

When Roalesk dies, proliferate, then proliferate again. (Choose any number of permanents and/or players, then give each another counter of each kind already there. Then do it again.)

Whenever a Merfolk you control deals combat damage to a player, draw a card.

Shaper Apprentice has flying as long as you control another Merfolk.

{3}{G}: Put a +1/+1 counter on target creature.

{2}{U}, Remove a +1/+1 counter from a creature you control: Draw a card.

As an additional cost to cast this spell, reveal a Merfolk card from your hand or pay {3}.

When Silvergill Adept enters the battlefield, draw a card.

(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.

Flash

When Swift Warden enters the battlefield, target Merfolk you control gains hexproof until end of turn. (It can't be the target of spells or abilities your opponents control.)

Tishana, Voice of Thunder's power and toughness are each equal to the number of cards in your hand.

You have no maximum hand size.

When Tishana enters the battlefield, draw a card for each creature you control.

When Vineshaper Mystic enters the battlefield, put a +1/+1 counter on each of up to two target Merfolk you control.

+1: Look at the top four cards of your library. You may reveal a creature or land card from among them and put it into your hand. Put the rest on the bottom of your library in a random order.

-3: Destroy target artifact, enchantment, or creature with flying.

-8: You get an emblem with "Creatures you control get +2/+2 and have vigilance, trample, and indestructible."

You may cast creature spells as though they had flash.

+1: Until your next turn, up to one target creature gains vigilance and reach.

-2: Look at the top three cards of your library. Exile one face down and put the rest on the bottom of your library in any order. For as long as it remains exiled, you may look at that card and you may cast it if it's a creature spell.

When Watertrap Weaver enters the battlefield, tap target creature an opponent controls. That creature doesn't untap during its controller's next untap step.

At the beginning of your end step, untap all lands you control.

This spell costs {1} less to cast if you control a Wizard.

Counter target spell.

When Zegana, Utopian Speaker enters the battlefield, if you control another creature with a +1/+1 counter on it, draw a card.

{4}{G}{U}: Adapt 4. (If this creature has no +1/+1 counters on it, put four +1/+1 counters on it.)

Each creature you control with a +1/+1 counter on it has trample.