Overlord(Boss)

Overlord is a massive mech suited with a great variety of visible weaponry, which is presumably attached to the top of the arena when you first encounter them by several large tubes. Overlord is the only boss of Sanctum, and is normally the first final boss that players encounter. In normal mode, their face is covered with a mask, which in hard mode, is removed to reveal an eye beneath inside the fleshy matter around it. Overlord's fight is mostly characterized by being heavily scripted and consistent.

For information about the ship with the same name as this boss, see Overlord (Ship).

Attack Patterns
Overlord has three distinct phases, each of which having its own health bar, each with less health than the last. Overlord's attack patterns are highly scripted and often loop upon themselves in the same sequences, although are independently subject to some variation depending on where the player is in the arena when any given attack is being used.

Phase 1
Phase 1 begins with Overlord being invisible, then appearing from the dark background, beginning the fight shortly after they're fully visible. Overlord's attacks loop in the same sequence until this phase's health is depleted.

Upon reaching 0 health in this phase, many portions of the mech are blasted off of Overlord as well as their tubing in a short cinematic, throwing them backward and onto the floor of the arena, which now appears to be old, torn up metal plating in the background. Overlord then transitions into phase 2.

Phase 2
After the short period of Overlord's immunity described before, phase 2 begins.

Upon reaching 0 health in this phase, more portions of Overlord's mech are blasted off, leaving them floating around the top of the arena with just their torso. The background rises again, to show intricate carvings in the wall which bear 4 large holes aligned vertically.

Phase 3
After another short period of invulnerability, Overlord will begin attacking again, floating from side to side in the arena until the phase ends.

Upon reaching 0 health in this phase, Overlord will stop attacking, and will slowly descend and then violently explode, ending the fight, generating the normal boss drop and allowing the player to exit and end the run from where they came, or if the player has all 4 seals, proceed to floor 6 and continue the run.

At the end of the fight, if this is the first time a player has defeated Overlord, they will drop the first seal to floor 6, and will unlock the methods by which the player will receive the other 3 seals (Renegade's offer, Bloke's offer, and Kleines' offer).

=Notes=
 * Overlord is considered the first final boss of the game, as it's the furthest into the Facility a player can get on their first run and most new players are unlikely to encounter the other possibility so soon (note: big spoilers).
 * Overlord is just one of a series of mechs that were presumably created for war.