Ven is the commander of a Species 6339 ship in Infinite Regress, a survivor of a people ravaged by the Borg who demands the return of the virus-laden vinculum Voyager has salvaged.
Ven appears in the fifth-season Voyager episode Infinite Regress. His people, catalogued by the Borg as Species 6339, were all but destroyed by assimilation only a few years earlier.
In response they engineered a synthetic pathogen and sent volunteers to be assimilated while carrying it. The disease reached a cube's vinculum, the device that links drones' minds, and caused the cube to destroy itself. Ven intends the still-infected vinculum to be recovered by other Borg so that the sickness spreads.
Voyager has beamed the device aboard, where it is flooding Seven of Nine with the personalities of assimilated individuals. Ven refuses to wait while the crew try to disable it and opens fire, and Janeway gives it back only once Tuvok has freed Seven.