Hitting different levels opens up new abilities witch you should choose carefully before starting a match. A quick overview on what each captain ability does:
Health Crate - Unlocked: Level 2
Summoning the health crate will allow one of your soldiers to head towards it and replenish up to 50 health points.
Artillery - Unlocked: Level 7
Take this baby on the battlefield and you'll be able to call in an artillery airstrike that will land up to 10 squares away from your captain, and deliver a total of 28 damage points across a wide radius.
Deployo-Cover - Unlocked: Level 12
Found yourself in a sticky situation? Activate this ability to pull a defensive shield over your current square. It's capable of absorbing 150 damage points in total.
Less-Harma Pharma - Unlocked: Level 17
If it's all going horribly wrong, this ability provides a crate of pills which will reduce damage taken by 25% for a total of five turns.
Detecto-Sweep - Unlocked: Level 22
If you've found yourself handling a particularly sneaky swarm of enemies, then the Detecto-Sweep will allow you to reveal all objects and enemies currently hidden within a five square radius.
Team Spirit - Unlocked: Level 27
If a squad member has taken damage and remains in the line of fire, chuck 'em a bit of Team Spirit. This will not only heal the player by 30 points, it will also reduce the damage they take by 15% for three turns.
Orbital Strike - Unlocked: Level 32
This mighty strike from above will deliver up to 90 points of damage, spread across a three square range. Just make sure you're not anywhere nearby when you use it, eh?
Bee Bomb - Unlocked: Level 37
This vicious force of nature will place a bee hive up to six squares away, spewing out bees that will do up to 20 points of damage for the next eight turns.