The Advanced Ceph Assault Units, or otherwise known as "Guardians" are the most powerful of on-foot Ceph units in Crysis 2. They appear to be the original Ceph -- much like the ones at Tunguska -- as they possess the ability to cloak, which is not present in other Ceph warriors. Guardian Units drop 5,000 Nano Catalyst upon death (Crysis 2 only).