Enter the Unknown

Target creature you control 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 the creature, then put the card back or put it into your graveyard.)
You may play an additional land this turn.

Forerunner of the Heralds

When this creature enters, you may search your library for a Merfolk card, reveal it, then shuffle and put that card on top.
Whenever another Merfolk you control enters, put a +1/+1 counter on this creature.

Majestic Heliopterus

Flying
Whenever this creature attacks, another target Dinosaur you control gains flying until end of turn.

Ghalta, Primal Hunger

This spell costs {X} less to cast, where X is the total power of creatures you control.
Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)

Giltgrove Stalker

This creature can't be blocked by creatures with power 2 or less.

Hardy Veteran

During your turn, this creature gets +0/+2.

Hunt the Weak

Put a +1/+1 counter on target creature you control. Then that creature fights target creature you don't control. (Each deals damage equal to its power to the other.)

Jade Bearer

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

Jadecraft Artisan

When this creature enters, target creature gets +2/+2 until end of turn.

Jadelight Ranger

When this creature enters, 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.)

Jungleborn Pioneer

Merfolk

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

Knight of the Stampede

Dinosaur spells you cast cost {2} less to cast.

Wingbane Vantasaur

Naturalize

You Line Up the Shot

Martyr of Dusk

Vampire

When this creature dies, create a 1/1 white Vampire creature token with lifelink.

Orazca Frillback

Saproling

Overgrown Armasaur

Enrage — Whenever this creature is dealt damage, create a 1/1 green Saproling creature token.

Rivals of Ixalan