|“||Necrodeus hates light and wants to steep the world in darkness. As a pirate, I can respect that. But with no light, all my treasure would cease sparkling. And I can't have that. Do everything in your power to stop him. My gold must shine!”|
|— Daroach • Kirby Mass Attack|
Necrodeus is the main villain of Kirby Mass Attack. He also serves as the final boss in the game.
Necrodeus' head is a horned white skull with lustrous red eyes. He seemingly has a third eye socket in the middle of his forehead, but no eye is seen within. Necrodeus has two curved horns on the sides of his head and a smaller, straight third horn on its top. Inside his mouth lies a set of sharp fangs, and he has an uncharacteristically wacky-looking clown nose. His body is made of purplish black smoke, which during the beginning cutscene almost resembles Nightmare's cloak. Around his neck is a necklace made completely out of Skully-like skulls. Matching the rest of his cadaverous features, his hands are skeletal and can come together to create a red eye-like marking on his wrists.
He initially wields a black staff with a purple jewel in its top which he uses to decimate Kirby at the beginning of the game, but swallows it in preparation for the final confrontation, requiring Kirby to destroy him in order to retrieve it. As the final battle concludes, his true form is revealed to be a purple Zero-like eye (especially similar to its small red core) that lies within the jaws of his skull.
As Kirby nonchalantly explores the southern reaches of Pop Star, a "skull-faced fiend" comes into view and blocks out the sky with a cover of ominous dark clouds. The fiend is instantly identified as Necrodeus, the grievous leader of the Skull Gang, whose goal is to drown the planet's light in an endless sea of darkness.
Using his magic staff, he splits Kirby into 10 weak copies, which he deftly overwhelms until only one remains. Necrodeus disappears, unknowingly leaving the last Kirby to recover using his Heroic heart. Kirby sets out on his adventure to proclaim the staff to regain his former power.
Throughout the game Necrodeus uses his Skull minions to try and subdue Kirby rather than face him head on. This tactic is unsuccessful, and the Kirbys manage to annihilate the gang, ending with Skullord in Volcano Valley. With his hold on Pop Star weakened, he has no choice but to allow them into his stronghold in Necro Nebula.
Just as the Kirbys think they've claimed the staff, Necrodeus appears and absorbs it, setting the scene for the final battle. He is a multiple-phase boss with a wide array of attacks.
Many of his attacks can KO a Kirby in one hit. First, he will use his skeletal hands to smash the ground below him and try to close his palms around the Kirbys. He will also use his index fingers to produce sparks of electricity. The Kirbys must destroy the hands in order to progress to the next phase of the fight.
With only his head (and to an extent his torso) left, he will begin by spitting out metal mines that shoot lasers in different directions. These mines can be easily destroyed by Kirby before they produce lasers however. Necrodeus can also discharge large balls of electricity that bounce off of the screen and shoot off a blast of energy from his mouth. Necrodeus also has help from Skullions. Like normal Skullys, they will turn purple and attempt to snatch a Kirby from the player's grasp. If a Kirby is grabbed, the Skullion will float over to Necrodeus, who will devour the Kirby and eliminate it from the fight.
At this point, his weak point is the purple eyeball inside his mouth, which will occasionally reveal itself in the middle of attacks. If the eye takes enough damage, his skeletal helmet will crack and shake rapidly. If the head is subsequently attacked, the player will be required to tap as fast as they can. If the player is quick enough, Necrodeus' cranium will be destroyed and the battle will end.
Once Necrodeus is defeated his staff will appear, ending the game and allowing the 10 Kirbys and their heart to become one whole being again.
- Necrodeus seems to emit a deep metallic cackle in battle, making him the one of four final bosses to cackle during the fight against him, the other three being Drawcia, Marx, and Marx Soul.
- Necrodeus, Dark Mind, Wham Bam Jewel, and Magolor Soul are the only bosses in the series to have exactly three eyes.
- Necrodeus's appearance changes from the cutscenes to the boss battle; he gains hands with a less "boney" appearance, his horns are a bit more curvacious, and his shadowy cloak is smaller, as well as having a smaller nose and more promient teeth.
- If a Kirby is lost to Necrodeus and the other Kirbys succeed in defeating him, a white Kirby with angel wings will appear in the cutscene after Necrodeus' destruction.
- Necrodeus is the only undead final boss in the series whose living form is never seen or attacked by Kirby.