To recruit Lynn into your party, have Karl (engineer) in your party while doing a mission or, preferably, a random skirmish. If he unlocks his potential during the battle, Lynn should be recruited for your use in future missions.
Unlockable: Characters
Below are a list of some of the characters that can be unlocked for use during the course of the game.
Audrey - Earn ten medals
Emile - Let Oscar die in battle after unlocking his true potential
Knute - Enter the Command Room with a million DCT
Musaad - Beat the game once through in its entirety
