Mzugru, Security Drone is the first secret boss in Graven Deep.
How to Find the Mzugru, Security Drone Boss in Graven Deep
Follow the path at the start of the dungeon. After the first couple of trash packs, there will be a trail leading to the right. At the end of the trail is a door in the floor called Security Depot. Inside the room, you will need to activate several control knobs in the correct order to summon the boss. Defeating this boss gives you a buff called Shield Generator, increasing your max health by 10% and giving you 50% damage mitigation for 3 seconds when you take damage (40 second cooldown).
How to Defeat Mzugru, Security Drone Boss in Graven Deep
This boss has around 3 million HP. It's quite an easy boss, but there are a couple of things to watch out for:
Lightning Bolts
He shoots lightning bolts into the air. These land after a couple of seconds, creating lightning AOEs which should be avoided.
Pylons
The boss will be shielded and healed by the pylons around the sides of the room. When this is happening, the boss is immune to all damage so you should focus on the pylon that is channeling.
Spin Attack
The boss also does a spin attack. DDs and healers should step back to avoid this.