Other Merfolk you control get +1/+1.

Mist-Cloaked Herald can't be blocked.

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

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.)

(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.

Counter target noncreature spell. Its controller creates two Treasure tokens. (They're artifacts with "{T}, Sacrifice this artifact: Add one mana of any color.")

Counter target creature spell.

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

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

{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.

({T}: Add {G}.)

({T}: Add {U}.)