These unfortunate individuals were once krogan. After capture, experimentation, and attempts at exaltation, they are now Behemoths, bearing the characteristic white carapace of the kett and the strength of a krogan in full fury.
Behemoths appear to be an early attempt at exaltation, and the process for the krogan is as yet unrefined. Unlike exalted angara, whose transformation is genetically and neurochemically stable, Behemoths are unable to produce enough serotonin to break out of the feedback loop that results in krogan blood rage, rendering them permanently aggressive and non-communicative. In addition, DNA samples suggest Behemoths are susceptible to hypothalamic tumors, further evidence that exaltation is intended to affect the body's oxytocin production and social bonding responses.
Fighting a Behemoth is not for the unprepared. With a krogan's resilience to gunfire and a preference for charging into melee, APEX tactics currently revolve around multiple rocket-propelled grenades.