Ravagers are former rachni that the Reapers have transformed into heavy artillery through a process of implantation and genetic modification. As walking organic turrets, they can sustain and inflict considerable damage.
Ravagers bear egg sacs that continuously spawn swarmers. If the sacs are destroyed, either during combat or upon the ravager's death, their entire contents burst forth to charge the enemy and explode on contact. A dead ravager expels a caustic gas and an acidic puddle.
Alliance scientists have theorized that it is easiest for the Reapers to maintain control over units of rachni genetic extraction because of the species' neurological predisposition for hive-mind consensus.