Deep sea guard
Deep Sea Guard is a valuable ally, in that for 2 energy (1 blue and 1 colorless) you get a creature with 2AP and 3 HP. Deep Sea Guard also has the added bonus of being equally strong defensively while still attacking, being the only ally who does not exhaust when it attacks. This is extremely useful early in the game, and can be combined with cards like Develop to be a very powerful threat.

Strong against: aggro and quantity decks.

Weak against: 3AP/3HP or larger allies.