Siren Stormtamer

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

Faceless Haven

{T}: Add {C}.
{S}{S}{S}: Faceless Haven becomes a 4/3 creature with vigilance and all creature types until end of turn. It's still a land. ({S} can be paid with one mana from a snow source.)

Mana Leak

Counter target spell unless its controller pays {3}.

Essence Capture

Counter target creature spell. Put a +1/+1 counter on up to one target creature you control.

Merfolk Trickster

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

Tempest Djinn

Flying
This creature gets +1/+0 for each basic Island you control.

Archmage's Charm

Choose one —
• Counter target spell.
• Target player draws two cards.
• Gain control of target nonland permanent with mana value 1 or less.

Insectile Aberration

Delver of Secrets

At the beginning of your upkeep, look at the top card of your library. You may reveal that card. If an instant or sorcery card is revealed this way, transform Delver of Secrets.

Delver of Secrets // Insectile Aberration

Tormod's Crypt

{T}, Sacrifice Tormod's Crypt: Exile target player's graveyard.

Counterspell

Scry 1. (Look at the top card of your library. You may put that card on the bottom.)
Draw a card.

Snow-Covered Island

Spell Pierce

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

Remand

Counter target spell. If that spell is countered this way, put it into its owner's hand instead of into that player's graveyard.
Draw a card.

Mystical Dispute

This spell costs {2} less to cast if it targets a blue spell.
Counter target spell unless its controller pays {3}.

Aether Gust

Choose target spell or permanent that's red or green. Its owner puts it on their choice of the top or bottom of their library.

Vendilion Clique

Flash
Flying
When Vendilion Clique enters, look at target player's hand. You may choose a nonland card from it. If you do, that player reveals the chosen card, puts it on the bottom of their library, then draws a card.

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.