Deeproot Warrior

Whenever Deeproot Warrior becomes blocked, it gets +1/+1 until end of turn.

Unknown Shores

{T}: Add {C}.
{1}, {T}: Add one mana of any color.

Shaper Apprentice

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

Kumena's Speaker

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

Vow of Flight

Enchant creature
Enchanted creature gets +2/+2, has flying, and can't attack you or planeswalkers you control.

Tempest Caller

When Tempest Caller enters, tap all creatures target opponent controls.

Soul of the Harvest

Trample
Whenever another nontoken creature you control enters, you may draw a card.

Shapers of Nature

{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.

Jungle Barrier

Defender (This creature can't attack.)
When Jungle Barrier enters, draw a card.

Concentrate

Time Warp

Target player takes an extra turn after this one.

Island

Rancor

Enchant creature
Enchanted creature gets +2/+0 and has trample.
When Rancor is put into a graveyard from the battlefield, return Rancor to its owner's hand.

Giant Growth

Target creature gets +3/+3 until end of turn.

Vineshaper Mystic

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

River Sneak

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

Prey Upon

Target creature you control fights target creature you don't control. (Each deals damage equal to its power to the other.)

Aether Gale

Return six target nonland permanents to their owners' hands.

Threads of Disloyalty

Enchant creature with mana value 2 or less
You control enchanted creature.

Forest

Merfolk Sovereign

Other Merfolk creatures you control get +1/+1.
{T}: Target Merfolk creature can't be blocked this turn.

Waker of the Wilds

{X}{G}{G}: Put X +1/+1 counters on target land you control. That land becomes a 0/0 Elemental creature with haste. It's still a land.

Prismatic Lens

Watertrap Weaver

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