Complete the indicated task to recruit the corresponding fighter.

Cruz: Rescue Cruz in the level BF23.5 bonus level.
Durant: Stand next to him in level BF3 to rescue him.
Elena: Recruited at the start of level BF27.
Nietzsche: Move down two squares from Durant's location in level BF6 to unlock the hidden map. Then enter the town located three squares to the right to recruit Nietzsche equipped with the Coral Spear. If you already completed level BF Nietzsche will still join you but will not have the Coral Spear.
Rosary: Defeat Roswell in level BF10. Rosary will join you in level BF11B.
Roswell: Defeat Rosary in level BF10. Roswell will join you in level BF11A.
Russell: Defeat Aegina and complete level BF20. Then, rescue Russell in level BF21.