Other Merfolk get +1/+1 and have islandwalk. (They can't be blocked as long as defending player controls an Island.)

Flash
Flying
When this creature enters, choose up to one target creature spell or planeswalker spell. Its owner puts it on their choice of the top or bottom of their library.
Evoke—Exile a blue card from your hand.

Equipped creature gets +0/+3.
Astral Projection — : Equipped creature phases out. (Treat it and anything attached to it as though they don't exist until its controller's next turn.)
Equip

: Exchange control of this artifact and target nonland permanent.

Delayed Blast Fireball deals 2 damage to each opponent and each creature they control. If this spell was cast from exile, it deals 5 damage to each opponent and each creature they control instead.
Foretell (During your turn, you may pay and exile this card from your hand face down. Cast it on a later turn for its foretell cost.)

Vigilance, trample, haste
This creature enters with X +1/+1 counters on it.
When this creature dies, create a number of tapped Treasure tokens equal to its power.

Put target artifact or creature card from a graveyard onto the battlefield under your control. Shuffle Beacon of Unrest into its owner's library.

First strike

Flying, protection from black
Echo (At the beginning of your upkeep, if this came under your control since the beginning of your last upkeep, sacrifice it unless you pay its echo cost.)
When this creature enters, return target creature card from your graveyard to the battlefield.

Attacking creatures you control have deathtouch.
Whenever a creature you control deals combat damage to a player, draw a card.

This land enters tapped unless you have two or more opponents.
: Add or .

Enchant creature
Enchanted creature can block any number of creatures.

Whenever this creature deals damage to a creature, put a third-degree-burn counter on that creature. It gains "At the beginning of each end step, sacrifice this creature unless you scream 'Aaah!' at the top of your lungs."

As an additional cost to cast this spell, sacrifice a green creature.
Search your library for a green creature card, put it onto the battlefield, then shuffle.

(: Add .)

If one or more +1/+1 counters would be put on an artifact or creature you control, that many plus one +1/+1 counters are put on it instead.
, : Put a +1/+1 counter on target artifact or creature you control. Activate only as a sorcery.
Cycling (, Discard this card: Draw a card.)

Enchant creature
Enchanted creature gets +2/+2 and has "Whenever this creature attacks, untap all lands you control."
Umbra armor (If enchanted creature would be destroyed, instead remove all damage from it and destroy this Aura.)

Permanents you control gain hexproof and indestructible until end of turn.

Whenever this creature or another Elemental you control enters, look at the top card of your library. If it's a land card, you may put it onto the battlefield tapped. If you don't put the card onto the battlefield, put it into your hand.

Station (Tap another creature you control: Put charge counters equal to its power on this Spacecraft. Station only as a sorcery. It's an artifact creature at 20+.)
10+ | Whenever you attack, Dawnsire deals 100 damage to up to one target creature or planeswalker.
20+ | Flying