Velikan is the new secret boss found inside Building 21; an alert notification will pop-up on your screen towards halfway through the DMZ match. Velikan’s location will always be at the center room on the second floor of Building 21.
Once confronted, he will relentlessly pursue your squad with a grenade launcher until he is killed. Killing him will drop the Black Key Access Card and a RGL-80 Grenade Launcher – which you can safely store in your weapons stash as a contraband weapon after a successful exfil.