Briarberry Cohort

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

Forest

Gilt-Leaf Alchemist

Cerulean Wisps

Target creature becomes blue until end of turn. Untap that creature.
Draw a card.

Consign to Dream

Return target permanent to its owner's hand. If that permanent is red or green, put it on top of its owner's library instead.

Counterbore

Counter target spell. Search its controller's graveyard, hand, and library for all cards with the same name as that spell and exile them. Then that player shuffles.

Cursecatcher

Sacrifice this creature: Counter target instant or sorcery spell unless its controller pays {1}.

Deepchannel Mentor

Blue creatures you control can't be blocked.

Drowner Initiate

Whenever a player casts a blue spell, you may pay {1}. If you do, target player mills two cards.

Faerie Swarm

Flying
Faerie Swarm's power and toughness are each equal to the number of blue permanents you control.

Flow of Ideas

Ghastly Discovery

Draw two cards, then discard a card.
Conspire (As you cast this spell, you may tap two untapped creatures you control that share a color with it. When you do, copy it.)

Barrenton Medic

{T}: Prevent the next 1 damage that would be dealt to any target this turn.
Put a -1/-1 counter on this creature: Untap this creature.

Isleback Spawn

Shroud (This creature can't be the target of spells or abilities.)
This creature gets +4/+8 as long as a library has twenty or fewer cards in it.

Kinscaer Harpoonist

Flying
Whenever this creature attacks, you may have target creature lose flying until end of turn.

Knacksaw Clique

Flying
{1}{U}, {Q}: Target opponent exiles the top card of their library. Until end of turn, you may play that card. ({Q} is the untap symbol.)

Shadowmoor