Players going through this can unlock new challenges, powers and abilities and even elite units. (impulsegamer.com)
Challenge mode takes story areas and adds in only elite units, or combines bosses together. (darkstation.com)
As in the story you read, many of the battles are fought by elite units of Exodrones — these cybernetic super-soldiers are a graft of heavily augmented organic tissue and machine that are grown and manufactured as empty shells, possessing no life of their own. (gristmillstudios.com)