Hidden Mechs:

Select a Trials of Grievance instant action mission. Changing your name in the Star configuration screen to Calvin (case sensitive) to add the Elemental between Dire Wolf and Fire Moth. Change your name to Hobbes (case sensitive) to add the Tarantula between Elemental and Fire Moth. Change your name to Enzo (case sensitive) to adds the Battlemaster IIC between Tarantula and Fire Moth (latest version patch required).