MevNav was long ago a mercenary corporation of Mevy that also served as the official navy of Mevy. MevNav is one of the oldest militaries on Terrahypt, dating back to the zeranian era. After Yluxa, their defenses got vastly crippled and allowed for criminals to infiltrate and take over the navy.
Before the invasion, the technology the infiltrators had at their disposal was substantially less lethal. Now, their weaponry have gone from projectile to plasma, using blasters and railguns that fire dense packets of mercury ions at their enemies. They are also armed with missiles of which they have no shortage of.
Despite MevNav's ominous behavior, Terrahypt has no plans to remove them together with Mevy from the Zerzek. They are considered as exiles within the desert and pose no real threat to the Terrahyptian civilization.