Briarberry Cohort

Flying
Briarberry Cohort gets +1/+1 as long as you control another blue creature.

Island

Faerie Seer

Terror

Destroy target nonartifact, nonblack creature. It can't be regenerated.

Sea Sprite

Faerie Duelist

Flash
Flying
When Faerie Duelist enters, target creature an opponent controls gets -2/-0 until end of turn.

Doom Blade

Snaremaster Sprite

Flying
When Snaremaster Sprite enters, you may pay {2}. When you do, tap target creature an opponent controls and put a stun counter on it. (If a permanent with a stun counter would become untapped, remove one from it instead.)

Counterspell

Mocking Sprite

Flying
Instant and sorcery spells you cast cost {1} less to cast.

Swamp

Consider

Surveil 1. (Look at the top card of your library. You may put it into your graveyard.)
Draw a card.