"You are able to mount the Siege Devourer and take control of it. Doing so will replace your skills with those to command the Siege Devourer." Siege Devourers have 1000 health and 25 energy. Your energy regeneration is based on your class and equipment (i.e., a weapon with +15 energy and -1 energy regeneration will not provide the energy bonus, while still reducing your energy regeneration). They are enemies in the bonus mission, Gwen's Story.