Extra Final Boss

The Extra Final Boss, or the Extra Final Boss Battle, or The Crown is the true final level of The One Billion Survivor and also the last level of the official Story Mode. It precedes Stage 8 and only found in Extra Mode. The Extra Final Boss is also available in The True Arena, served as Round 20. Two variations of the Extra Final Boss are Normal and Hard.

Variations
The Extra Final Boss is much harder than the previous 8 extra stages after all the Fright Zone Challenges completed and all the other sub-games.

Normal Extra Final Boss
The Normal Extra Final Boss is the level that the Underground Nation traps into another dimension.

Phase 1
Phase 1 of the Normal Extra Final Boss, he makes a dimension to a hard arena.

Phase 2
After Phase 1's normal defeat, he resurrects himself to Phase 2. The only way to destroy is using Magic Destruction.

Hard Extra Final Boss
The Hard Extra Final Boss is the variation level that the Underground Nation upgrades himself to the ultimate version of The One Billion Survivor, the Ultimate ThroneMaster Nation XX DX+ Soul. He is also the hardest boss, after Stage 8 EX.

Phase 1
Phase 1 of the Extra Final Boss is simple, his wings are darker than Star Dream Soul OS's and his magic is extremely strong. He is called the Ultimate Thronemaster Nation Prime.

Phase 2
Phase 2 of the Extra Final Boss is harder, he does the same way as Star Dream's second phase, except he fires lasers, machine guns, and signal fire/ice pieces.

Phase 3
Phase 3 reprograms the Extra Final Boss, he upgrades to the Ultimate Thronemaster Nation Prime 2. Instead of firing two lasers, he fires 24 lasers of his primary attack. He also shoots ink missiles at the player.

Phase 4
Phase 4's core is called Master Nation. Master Nation is a merged version of Void and Void Soul from Kirby Star Allies. He is the Chaos King remixed by the evil Dr. Victor 2.0.

Phase 5
This is the game's true final boss. The ThroneMaster Nation transforms into an ultimate throne king, beating King Resistance and the Leading Corrupt Corporate Executive. Phase 5 is the final part of the final boss, he upgrades to the ultimate version, ULTIMATE THRONEMASTER NATION XX DX+ Soul, with a whopping 80 billion health. As his health bar goes down to 40 billion, he has Void Termina's healthbar instead. The team powerup must destroy the Jevil shield in order to defeat the ThroneMaster. To make sure you can safely attack, you must wait until he fires 20 lasers, and cool down, but this will actually take a while as this boss battle after completing the whole game has 240 billion health. This is probably the hardest boss battle, beating the Normal Extra Final Boss. Also, the ThroneMaster will explode once the boss is defeated. It is bigger than his defeat, and after that he will be absorbed, saving Barry's dance group.

Finishing the Extra Final Boss
Finishing the Extra Final Boss battle with the Glitter Force, the Doki Doki Glitter Force, the Cosmic, the DSPE, and the XX Group gets 100% of any file. Also, when finishing the level, the player unlocks two secret live performing videos, "Glitter Force Character Live Show" and "Glitter Force Character Live Show 2.0".

Nightmare Mode
Nightmare Mode is added in version 2.05, but it was improved in 2.07.

This was also changed in version 3.01.0 by upgrading the true final boss.

Trivia

 * The Extra Final Boss is not included in The One Million Survivor, because of serious problems. This was fixed and added in version 3.0 of the lite version, with less health.
 * When finishing this level as the XX Group, the PIU contest group (Twist of Fate, HTTP, Up and Up, Travel to Future, and Rave 'til the Earth's End), the RB Twins, and the Dancer Survival Powered Executives, the player will get 100% of any file.
 * Finishing the Extra Final Boss with Barry Steakfries, the RB Twins, the Dancer Survival Powered Executives, Erica, Lucy, Prima, Mari, Miya, Glitter Lucky, Glitter Sunny, Glitter Peace, Glitter Spring and Glitter Breeze destroys the boss battle immediately after Phase 5 and gets 100% of any file. The explosion is bigger and stronger after his defeat.
 * Also, when the player finishes a 100% file, the staff credits will be the same as The Haunted House: Secret of the Ghost Ball ending, but has 2 languages. First is in Korean, then to English. The staff credits will move on to Fight and Flight.
 * Beating this level, will cause Erica, Lucy, Prima, Mari and Miya to get teleported back to Survival Land.
 * Finishing the Extra Final Boss, causes to unlock Pump It Up XX, Glitter Force and the 5 Minecraft Original Videos.
 * This has been changed since 3.02.0; it was moved to Stage 9.
 * The Hard Extra Final Boss is not included in Normal Story Mode once it was moved to Stage 8 EX nor The True Arena.
 * Shockingly, the Hard Extra Final Boss is added in version 2.01.0.