After making your way through the first three sections of the Secret Vault - Residence Area, Attis enters the hub arena and wants the Initiate's keycard to the Vault's laboratory. Obviously, the Initiate won't give it up freely, and the first Attis boss battle unfolds.
Attis is a mutant General, and he packs enough firepower that he doesn't need the army he's got with him. Look for the control console in the northeast corner of the room to reprogram the security robots to fight on your side. To unleash them, use the terminal to the south. Keep some distance attacking him while keeping in mind that laser based weapons have no effect.
Just when you think you've beaten Attis, he starts playing dirty. His mutant thugs overtake you and Attis lops off one of your arms to keep as a souvenir. He
then hurls you into the abyss.