Kalibas

Kalibas appears in the Nekravol level as a miniboss battle like Doom Hunters.

Appearance
Kalibas is a massive brain like demon in the same vein as the Spider Mastermind and the Arachnotrons, however unlike them Kalibas is completely immobile, it is surrounded by specialized turrets which help defend it and has a protective force field.

History
Kalibas is stated to be the decider of souls and whether or not they are discarded or tortured into Argent Energy and transformed into demons. It's stated as a ancient and high ranking demon that's extremely rare.

Combat Analysis
Kalibas is a powerful demon and acts similarly to a boss battle and has multiple phases:

Within its first phase it will fire purple fireballs from one of its 4 turret stands which guard the actual demon itself and will swap between each other at random and shield themselves, the area also has shifting platforms which lower into lava and fire blowing floors to add more pressure, it's also protected by a force field that completely protects it from all forms of damage until the turrets are destroyed.

Once one turret is destroyed it will switch to Phase 2 where it summons Gargoyles to defend it.

In Phase 3 after the 2nd turret has been destroyed it will spawn in Pain Elementals to defend it alongside the Gargoyles.

Phase 3 is repeated until all turrets are destroyed in which the shield protecting Kalibas will lower and demons will stop spawning and the Slayer can melee Kalibas, shattering the brain demon to pieces to proceed through the rest of the level.