Monolith

Monolith is the boss of Floor 6 on hard mode, and is considered the true final boss of the game. Monolith appears as a white, rounded, diamond-shaped construct with a red orb in the middle, large wings of white fire, and a series of runes behind it, arranged in a circle, that quickly orbit it. Monolith is the form that Null takes after killing Machine and claiming Power Eternal. Monolith is one of the few bosses that opens up room in the HUD, allowing for more screen space during the fight.

Attack Patterns
Monolith has three distinct phases, each with several attacks, a few attacks of which from phase 1 are copied and significantly upgraded in phase 2. Many of Monolith's attacks mimic that the functions of weapons that can be used by the player's ship. Some weapons were added after Monolith, and do not have attacks corresponding with their functions. Attacks for phase 1 are chosen randomly from a pools of attacks, while attacks in phase 2 are semi-random (explained further in that section), and phase 3 has a pool of attacks that are ordered and loop until half way through the phase, after which another unique attack begins and continues until Monolith's death. Monolith does not deal contact damage.

The fight with Monolith is incredibly fast, each attack often taking only a couple seconds to finish and to transition to the next attack. Monolith is also incredibly agile, dashing across the screen constantly for most of the battle.

Phase 1
After a short cutscene, Monolith explodes upward and begins a rapid ascent of the corridor the player would normally see on the death screen.

Phase 2
After reaching 2/3 health, the death corridor breaks open with smoke falling from the top of the screen, into the sky above the city situated on top of the facility, with the spires in the intro cutscene of the game in the foreground. In this phase, Monolith switches between different "weapons", which determine the attacks it can use. The 12 attack patterns in this phase are split into 4 groups (the "weapons"), each with 3 patterns. At the start of the phase Monolith does a brief weapon-equipping animation and then does 3 attacks from one of the groups, though they don't have to be 3 different attacks. After the third attack, it equips a new weapon and does 3 attacks from a new group, continuing this pattern until phase 3. It's worth noting that the weapon-switching analogy is used somewhat loosely; the attack patterns in each group often use different weapons, such as one group containing a sword, razor, and runic attack.

Phase 3A
After reaching 1/3 health, Monolith rises further into the sky with smoke falling from them for a short moment, revealing an arena that appears as a landscape of bright clouds illuminated by the sun in the sky. A unique music track plays for this phase separate to the one that plays in phase 1 and 2. The attacks in this phase are always in the order shown, and cycle endlessly until a low enough health threshold is reached.

Phase 3B
Half way through phase 3, Monolith ends the previous cycle of attacks and begins another screen filling attack that continues until Monolith's death.

Cutscenes
When the player triggers the boss fight for floor 6 on hard mode, the room is instead empty, and without a boss fight. When the player descends to the next floor and enters the room where the conduit to power eternal would normally be, a short cutscene begins instead where the player finds Null on the other side of the arena, upside down. Shortly after, they flip over, and a large shell forms around Null and runes circle in from beyond the arena as the screen subtly rumbles. Null explodes upward and gains wings of white flame, and the battle begins.

After Monolith's health reaches 0, Monolith's shell falls away to reveal Null again, and both Null and D-13 (or whatever other ship) fall downward. If the player doesn't have the Integer Overflow cartridge, the player will be returned to the room they found Null in, and can continue to the next room, where D-13 finds the conduit and destroys it, the screen cutting to black as D-13 shoots at the conduit and then showing smoke billowing from a hole in the ground. Afterwards, credits roll, showing many of the enemies and bosses from the main 6 floors, and finally D-13 at the end who instead of falling past the bottom of the screen, dashes upward and beyond the top of the screen. Another music track plays, and D-13 is shown inspecting the corpse of Null, D-13 shortly after shaking and falling to the ground beside Null. The two pan downward, showing the city beyond them a bright, cloudy sky, with souls rising from the ground and into the sky. Null and D-13's bodies vanish into smoke, and their souls rise upward as well.

If the player defeats and ends the run at Monolith while playing as D-13 and gets an Exalted rank (S Ranks in all categories) on the results screen, an extra scene of dialogue will play between two people:

(A short pause) (A short pause) (A long pause) (A long pause) (A short pause) (A long pause)
 * 1: Hey, have you zoned out again?
 * 1: Jeez.
 * 2: Sorry, I was just thinking.
 * 1: First time for everything I guess.
 * 2: Hey!
 * 2: I'm trying to be serious here.
 * 2: Say.
 * 2: What do you want to do after the war is over?
 * 1: I don't know.
 * 1: I've never given it much thought.
 * 1: It's strange, now that I think about it. I never thought I'd see it end.
 * 1: Heh.
 * 1: I think I have an idea.
 * 1: After we take the facility, let's get up those spires.
 * 1: We can watch the sunrise.
 * 2: Hahaha. That's so tacky.
 * 1: Well?
 * 2: That better be a promise.
 * 2: Wait, I know. You can hold onto this for me.
 * 1: Huh, is that a watch?
 * 2: Don't worry, it doesn't work. And it's not like I'd need it anyway.
 * 2: It's more of a family heirloom.
 * 2: I thought you could keep it for, I don't know, good luck?
 * 1: ...
 * 2: Just come back safely OK?
 * 1: Yeah.
 * 2: Heh. Now you zoned out.
 * 1: N-No, I'm just tired. I should really get some sleep.
 * 1: You too. Tomorrow's the big day.
 * 1: I'll see you later.
 * 2: Goodbye Null.

After this ending, the award table in the hub will have a gold watch hanging off the side of it from under the trophies. The extra dialogue will not play if you achieve a floor 6 exalted run with another character, but you will still be granted the watch.