Deeproot Elite
{1}{G}
Creature -- Merfolk Warrior
1/1
Whenever another Merfolk you control enters, put a +1/+1 counter on target Merfolk you control.
Forerunner of the Heralds
{3}{G}
Creature -- Merfolk Scout
3/2
When ~this~ 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~.
River Sneak
{1}{U}
Creature -- Merfolk Warrior
1/1
~this~ can't be blocked.
Whenever another Merfolk you control enters, ~this~ gets +1/+1 until end of turn.