Tempest Djinn

Flying
Tempest Djinn gets +1/+0 for each basic Island you control.

Nightveil Sprite

Flying
Whenever Nightveil Sprite attacks, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Mist-Cloaked Herald

Chart a Course

Draw two cards. Then discard a card unless you attacked this turn.

Warkite Marauder

Flying
Whenever Warkite Marauder attacks, target creature defending player controls loses all abilities and has base power and toughness 0/1 until end of turn.

Merfolk Trickster

Flash
When Merfolk Trickster enters, tap target creature an opponent controls. It loses all abilities until end of turn.

Spell Pierce

Counter target noncreature spell unless its controller pays {2}.

Dive Down

Target creature you control gets +0/+3 and gains hexproof until end of turn. (It can't be the target of spells or abilities your opponents control.)

Essence Scatter

Wizard's Retort

This spell costs {1} less to cast if you control a Wizard.
Counter target spell.

Siren Stormtamer

Flying
{U}, Sacrifice Siren Stormtamer: Counter target spell or ability that targets you or a creature you control.

Exclusion Mage

When Exclusion Mage enters, return target creature an opponent controls to its owner's hand.

Island

Curious Obsession

Enchant creature
Enchanted creature gets +1/+1 and has "Whenever this creature deals combat damage to a player, you may draw a card."
At the beginning of your end step, if you didn't attack with a creature this turn, sacrifice Curious Obsession.