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Skeleton Boss
Blaster Master Zero artwork


Area 7




Acceleration Blast

This gargantuan mutant has nested itself inside the Planetary Depths Area. Like a parasite, it grows by devouring everything in its path, until one day the planet itself has nothing left to consume. A powered-up SOPHIA III may, just may, have a chance against this monstrosity...
— Skeleton Boss Description • Blaster Master Zero website

“The Planet Eater” Skeleton Boss is a boss in Blaster Master Zero, appearing as the mutant boss of Area 7. It later reappears twice in Area 9 as a normal enemy; the player is required to defeat the first one in order to access the rest of the area, however, the second one cannot be defeated, as the player doesn’t have access to Sophia Zero.

Physical Appearance[]

Skeleton Boss appears as the upper half of a skeleton of sorts. Its head has two curved horns and red eyes, a long neck with spines on each segment, shoulder blades that curve upward, a ribcage, and skeletal arms with pointed fingers. The rest of its body appears as that of a purple, organic-looking wall, which is the setting for Area 8.

General Information[]

Skeleton Boss appears as the mutant boss of the Subterranean Depths Area. Defeating it grants access to Area 8, as well as unlocks a shortcut through Area 7 for backtracking purposes.


Skeleton Boss is attached to the right side of the room; it can only move its head, which consistently wavers up and down. It can attack by charging up a large ball of energy from its mouth or by spitting out bouncing boulders. Each attack can be performed up to three times consecutively before Skeleton Boss switches moves or temporarily stops attacking. The boulders bounce at various different heights based on three variables: the location of Skeleton Boss's head upon spitting it out, a given vertical velocity, and a given horizontal velocity; this can make their trajectories difficult to predict.


Your Blaster Rifle won't even make a scratch against this mutant... But, if you could somehow use SOPHIA, you can do some real damage!
— Eve • Blaster Master Zero

Its attacks may not seem particularly threatening, but considering the player enters the boss arena without SOPHIA III, these can be particularly devastating if they cause Jason to fall off the platforms he needs to scale in order to access SOPHIA III, as falling from a height of four blocks or more is enough to die. As the boulders bounce fairly high, it is recommended to wait for Skeleton Boss to charge up its energy attack, or find a period of time when it isn’t attacking, to start scaling the platforms; from there, it’s an easy time to get SOPHIA III back into action.

Now that the player has access to SOPHIA III, Skeleton Boss can be damaged. Using the newly-acquired Acceleration Blast will cause a special sequence to occur, which results in the attack being able to defeat Skeleton Boss in one shot.

Alternatively, the player can defeat Skeleton Boss in a more traditional sense. The best strategy is to place a Shield Mine in front of its head and start shooting Crusher Shots diagonally up at it at point blank range, only stopping to replenish the Shield Mine when it terminates; Warhead Missiles can additionally speed this up if desired.

In Boss Blaster Mode, there are no longer any steps or elevator on the left side; the terrain is completely flat, although the spikes on the ceiling are still present. As there is no longer any place to easily hide, the Shield Mine at point blank range is the best strategy in said mode unless playing Co-op Boss Blaster Mode, in which case Acceleration Blast can be used by one player while the other drops a Shield Mine.

In Area 9, the first Skeleton Boss has reduced health. Furthermore, SOPHIA Zero's weapons are significantly stronger than SOPHIA III's, requiring only 2-3 shots from most weapons to take it down.

Destroyer Mode[]

While the Acceleration Blast sequence can still occur, it is considerably more difficult to perform, as when Skeleton Boss's boulders break, they release a red bullet aimed at the player, which goes through walls; it can be most easily performed by going back to where the lever is, as most of the bullets produced from the boulders breaking won't appear. Should the player manage to charge up the Acceleration Blast, it won't be nearly as effective due to the boss having more health and not being weak to it. Using the aforementioned Shield Mine strategy is the most viable, as it can destroy the boulders and the bullets they produce when destroyed, effectively nullifying all of Skeleton Boss's attack options.

In Area 9, the first Skeleton Boss has massively increased health, requiring 134 empowered Crusher Shots to destroy, and retains the Acceleration Blast resistance of its Area 7 version. The Shield Mine strategy is still effective as long as SOPHIA Zero is positioned such that any boulders which make it past one's empowered Shield Mine barrier go off-screen before releasing revenge bullets.


A variety of the mutant Jason encountered on Earth, "Skeleton Boss". It was originally meant to parasitize a planet's core and produce mutants to destroy the planet itself, but even the Cerbeboss couldn't withstand Stranga's harsh environment. Instead, it invaded a nearby planetoid and sends mutants it creates to Stranga from afar.
— Cerbeboss Description • Blaster Master Zero 2 website

“The Planet Destroyer” Cerbeboss is encountered in Area E on Planetoid E-3. When defeated, it drops the Access Key to Area F, where Planet Divido resides. The Cerbeboss looks like the Skeleton Boss in every way, but its body has a different color and has two extra heads.

The Cerbeboss attacks by firing spark-like projectiles from all 3 of its heads while the cyan head is in the foreground, shooting large fireballs that create a patch of large fire when they land while the grey head is in the foreground, or trails of lightning while the yellow head is present. The lightning trails do no damage themselves but are meant to propel Gaia-SOPHIA upward into spiked columns jutting from the arena ceiling; naturally they can instead be exploited for a Gaia System recharge from the drop back onto the floor. When any one head is brought below approx. 25% HP, Cerbeboss summons boulders from above while executing that head's attack --- these boulders, which can be destroyed for Capsules, are the only projectiles in the fight which can be nullified with Impact Wave.

If/once there is only one head left on the Cerbeboss, it will combine the attacks from the previous two heads for the rest of the fight, shooting a large lightning shot along the ground which then attempts to home in on Gaia-SOPHIA as a spark shot before plummeting to the ground and setting most of the floor ablaze.

Jason: "Cerbeboss"... It seems like a subspecies of the "Skeleton Boss" we fought back on Earth.

Eve: The three heads attacking together pose a big threat. It might be best to take them out one by one. And about those spikes on the ceiling... G-SOPHIA won't collide with them just by jumping normally, but I've still got a bad feeling... Jason, be careful, okay?

Jason: Got it. I can't be careless just because I've got G-SOPHIA.
— "Cerbeboss" Eve Chat • Blaster Master Zero 2

Cerbeboss is quite sturdy, requiring 60 G-Crusher Shots per head to destroy (180 shots for all 3 heads), and should be faced with whatever ordnance is on hand. Hexa Missiles will attempt to lock onto the skulls and vertebrae of the heads that are out of focus, but will ultimately slam into the in-focus head and body after whirling about. It is rematched as part of the boss rush beginning on Planetoid G-2, where it can particularly be humiliated with the Full Accel Burst in a throwback to the previous game's instant win option against Skeleton Boss.


  • Skeleton Boss seems to take on the role of the Plutonium Boss in Area 8 of Blaster Master. They both have visual similarities, such as being a head and torso stuck in a wall, having the ability to spit boulders from their mouths, and even the same name in Japanese, Skele Venom. With the last of those similarities possibly indicating that they're two different incarnations or forms of the same creature. However, the Skeleton Boss' role is not elaborated on much outside of its description on the Blaster Master Zero website and its apparent reappearance as Cerbeboss, whereas the role of the Plutonium Boss is expanded upon in Worlds of Power: Blaster Master, Blaster Master: Enemy Below, and Blaster Master: Blasting Again.
  • Skeleton Boss's and Venom Master's Japanese names, Skele Venom and Another Venom, respectively, seem to imply a relation between the two.

See Also[]