|This article contains information that does not coincide with the main series canon.|
|“||The final program has been activated. Its calculated victory probability is 99.9%. However, a small part of Haltmann's soul is yet to be purged, which could throw a wrench in its plans.”|
|— Vs. Star Dream Soul OS (Phase 1) • Kirby: Planet Robobot|
In its first phase, Star Dream Soul OS resembles its regular form in terms of body form: cylinder-shaped with a screw-like head. The biggest differences between OS and the original is the enormous, unhealed scar in its hull -inflicted by Galacta Knight and giving it a vaguely zombified appearance- and its color scheme, which is now mainly black, red, and beige. The pink lights coursing down the body now gradually vary from pink to golden. The shards on the wings are now slightly gray. Like its regular form, it is adorned with a heart symbol that has a crack down the middle.
In its second phase, Star Dream Soul OS is again very similar to its regular form. The pedestal linking the Mother Computer and the Access Ark mothership is gold, but there is very little difference otherwise. As the machine takes damage, however, it becomes clear that the faceplate of the machine planet is very different, with the color scheme identical to that of the original Galactic Nova.
In the fourth and final phase, Kirby is drawn into the very core of Access Ark, where he faces the heart of Star Dream Soul OS. The battle takes place in a dark circular chamber, with a mechanical heart in the center, similar to Galactic Nova Nucleus. In the first half of the battle, the circular battlefield is filled with energized pillars. In the second half, the heart has gone into battle itself, leaving the center of the chamber empty.
During Meta Knightmare Returns, Star Dream is seen in the background when fighting President Haltmann 2.0 in the Meta Knightmare Returns sub-game. When the president is defeated, the Mother Computer believes Meta Knight to be a new administrator and provides him with three tests of strength; when he defeats Dark Matter Clone and Sectonia Clone, the computer activates the Space-Time Transport program. This summons Galacta Knight, who promptly delivers an enormous slash to the machine, causing it to explode and sink below its platform. The seemingly fatal damage incurred by Galacta Knight causes a "final program" to be activated within the machine, eventually transforming it into Star Dream Soul OS to survive the otherwise lethal blow.
Star Dream Soul OS is first seen at the end of The True Arena. The computer once again attempts to destroy all life in the universe as it does in Story Mode; however, it has already consumed most of Haltmann's soul and, as implied by Star Dream (Phase 2)'s description from Story Mode, has forgotten its original purpose to bring eternal prosperity to the Haltmann Works Company by doing so. Late in the battle, Star Dream completely consumes Haltmann's soul, reducing the computer to a "cold, mindless machine" completely devoid of its Haltmann-derived sentience and bent only on mindless destruction.
Most of the battle against Star Dream Soul OS takes place in outer space, just outside of Planet Popstar's atmosphere. Kirby's Robobot Armor downloaded the Halberd's Scan Spec yet again, granting it Halberd Mode one last time. In addition to shooting small blasts with the Combo Cannon, Kirby can shoot apart a number of the computer's attacks, absorb the debris, and return fire in the form of stars. For the last portion of the fight, Kirby is swallowed into Access Ark's core, landing briefly unconscious. He awakens later as the inside of the ship flares to life. The 3D ring lights up, revealing Kirby's surroundings and the heart in the middle. Kirby will be left using whatever Copy Ability he may have to finish Star Dream Soul OS once and for all.
Star Dream Soul OS's attacks are largely similar to those of its normal mode counterpart, including launching missiles, suits of Invader Armor, and spiked hearts, and by opening holes in space that fire lasers (now larger and red rather than the purple of Star Dream's); the most conspicuous difference is that the malevolent machine now moves primarily by teleporting, an ability Star Dream's original form glaringly lacks. Star Dream teleports frequently and occasionally rushes at Kirby's ship, swinging around for a second strike when it does (in contrast to the original). When nearly half of its health is depleted, Star Dream Soul OS opens a portal that releases giant meteoroids, fires giant purple lasers, and creates a crystalline shield for itself. The shield can be destroyed by gunning down two heart-shaped objects holding it in place; Star Dream will flinch when one is destroyed, but will not take damage. While shielded, Star Dream Soul OS summons massive yellow-orange Code Cubes at Kirby's vessel and tries to ram it.
When its health bar is fully depleted, Star Dream Soul OS partially explodes and begins to fall from space, falling off the screen for a few seconds before reemerging with the Access Ark in tow, akin to the original battle.
Star Dream Soul OS, now merged again with Haltmann's massive base of operations, rises once again into space. The second phase begins with the newly born planet opening its entrance, and attempting to suck the Halberd in -- if Kirby gets pulled in, he gets struck with rapid lightning bolts, taking massive damage, and spat back out. The computer also inhales and spits out meteoroids, and opens black holes that fire laser-like waves. If the player takes too long to take out the first piece of the Access Ark, similar to its first phase, it will spin and attempt to ram Kirby. As the player damages Star Dream Soul OS, pieces of the Access Ark break off and sail toward Kirby.
As more pieces of the Access Ark break off, Star Dream Soul OS starts using new and old attacks. In addition to using attacks from its first phase, it creates the letters H, A, and L (a reference to HAL Laboratory), and sends them at the player. The Access Ark grows its limbs back and swings two of them at a time. It then detaches them once more of its health is depleted, causing them to sail past Kirby. It also dispenses Gigavolt II units and projects laser blasts.
When the front of the Access Ark has completely broken off, the inner layer is revealed: A massive, yellow Galactic Nova opens its eyes, emits a cat-like scream, and turns the space around it into a crystalline vortex. The machine kicks off the battle by firing giant purple energy lasers from its eyes and then spinning to sweep them across the screen. The machine proceeds to start a countdown -- it launches the numbers 5, 4, 3, 2, and 1 at the screen, all of which differ from the normal mode. The first three are launched much faster than before; the 2's change their spin direction to throw Kirby (and the player) off; and the 1 thrusts at Kirby, then retracts to rotate, thrusts again, and repeats the process several more times. After all of those, Star Dream Soul OS releases the messages, "GO!!" and "FATAL ERROR." If the player lets Star Dream Soul OS get this far, Kirby is bombarded by red walls for several seconds, which is very likely to defeat him outright unless he has full health and/or uses the dodge roll with extremely precise timing to minimize the impact. The countdown will reset to 5 should Kirby survive this attack.
In between countdown attacks, Star Dream Soul OS disappears and releases pieces of Galactic Nova to fight for it. These include (in order) two arrow-shooting weather vanes instead of one; three lightbulbs that fire strong electrical beams as opposed to two; piano keys that swirl around the screen; a pocket watch with teeth that tries to bite Kirby's vessel along with a spyglass that fires light beams; and a drafting compass that launches rings while spinning erratically.
After Kirby depletes Star Dream Soul OS's third health bar, a cutscene plays. The machine spits a laser at Kirby's vessel, downing it. Meta Knight detaches Kirby in his Robobot Armor just like in normal mode, but Star Dream isn't going to fall for the same finishing sequence twice. The manic machine takes a page from the pink puffball and starts inhaling, eventually ripping Kirby out of the armor and sucking him into its interior in a cruel twist of irony.
Kirby lands inside a large, dark area. The lights come on, revealing that Kirby is inside Star Dream Soul OS's core, an area fashioned after Galactic Nova Nucleus complete with an eerie remix of its theme. Pillars appear with multicolored objects suspended inside them and circle around the 3D ring while the heart occasionally spawns enemies. The pillars containing said objects are usually electrified, so Kirby will take damage if he touches them. The pillars also run into each other, sandwiching Kirby if he's caught in between.
When Kirby finishes breaking the objects, the heart - now completely devoid of both its sentience, sanity and almost any lingering trace of Haltmann - roars and engages Kirby itself. The now 'heartless' heart fires two pink energy lasers that sweeps the arena and create massive shock waves in their wake; shoots out Patas, Dacoogas, and Volms as explosive projectiles; and teleports in a circle around the room before warping above Kirby and firing two rounds of cutter blades, teleporting again if its health is low. As the heart's health drops, it also splits in half and dashes across the stage, creating stars and a massive explosion when its halves collide.
When Kirby completely depletes its health bar, the heart warps to the middle of the screen, pulses, and then releases several red shock waves as a final effort to defeat Kirby.The first shockwave covers the top of the screen. The second shockwave covers the middle of the screen. And the final shockwave consists of two energy waves that cover both the top and the bottom of the screen. These shock waves take out around 7/8 of Kirby's health and slam him into the screen; they cannot be blocked by defensive moves (such as the Leaf ability's Leaf Hide). However, it is still possible to avoid damage by performing a dodge, an air dodge, or simply by standing under the first two waves and jumping over the final wave. If Kirby survives, the heart utters one last Haltmann-esque groan and shatters, shutting both Star Dream and the Access Ark down for good.
|“||"Why did I reactivate such a terrible machine? Oh, I remember--I wanted to see her just one last time. How foolish! I should have known that no machine could make such a dream come true."”|
|— VS Star Dream Soul OS (Phase 2, 3, and 4 (First Half)) • Kirby: Planet Robobot|
|“||All of Haltmann's memories have been deleted from the OS. Even his soul--the last trace of Haltmann--has vanished. Star Dream has gone from a near-perfect being to a cold, mindless machine.”|
|— VS Star Dream Soul OS (Phase 4 (Second Half)) • Kirby: Planet Robobot|
|“||The final program has been activated. Its calculated victory probability is 99.99%. However, a small part of Haltmann's soul has yet to be purged, which could throw a wrench in its plans.”|
|— vs Star Dream Soul OS (Phase 1; European Version) • Kirby: Planet Robobot|
|“||All of Haltmann's memories have been deleted from the Mother Computer. Even his soul - the last trace of Haltmann - is gone. Star Dream has gone from a near perfect being to a cold, mindless machine.”|
|— vs Star Dream Soul OS (Phase 4; second half; European Version) • Kirby: Planet Robobot|
- With a total of four health bars, Star Dream Soul OS has the most health out of any boss in Kirby: Planet Robobot, and the most health out of any final bosses in the Kirby franchise thus far.
- Both Star Dream Soul OS and Star Dream make frequent use of heart shapes, even sporting a heart logo (with a crack down the middle) on its hull. This symbolizes President Haltmann's love for his daughter and grief that she was lost.
- Star Dream Soul OS is the third true final boss to engage Kirby in a surprise fight at the end of The True Arena, the first one being Marx Soul from Kirby Super Star Ultra, and the second being Soul of Sectonia from Kirby: Triple Deluxe.
- It is the second boss in The True Arena to have at least two direct phases with the same name, the first being Soul of Sectonia.
- Star Dream Soul OS is one of six final bosses who carry the word 'soul' in their names, but one out of seven final bosses to be resurrected in the series. The other six are Drawcia Soul, Marx Soul, Magolor Soul, Soul of Sectonia, Zero2, and Void Soul.
- Like Star Dream, the battle against Star Dream Soul OS's first three forms appears to pay homage to the battle against Gorgon in Star Fox 64. Star Dream Soul OS releases missiles and fires a giant laser into the center of the screen. When the Halberd Mode spins, lasers that hit it bounce off with a metallic sound, like an Arwing deflecting lasers with a Barrel Roll. Star Dream Soul OS's second and third forms teleport with an effect similar to that of Gorgon.
- The attack in which Star Dream Soul OS attempts to inhale Kirby, then spits multiple meteors at him, appears to pay homage to the battle against Andross in Star Fox 64 and Star Fox Adventures.
- Whenever a pillar inside Star Dream Soul OS is destroyed, President Haltmann's voice can be heard crying out in pain. After destroying the final pillar, the pause menu states that Haltmann was fully erased from Star Dream. It is implied that the pillars contained what was left of Haltmann, and Kirby was actually the one to destroy what was left of him.
- When the heart is finally shattered, a slower, lower pitched version of the same voice clip is played, seemingly implying that Haltmann's soul perished with his creation. The pause menu for this last phase states that Haltmann's soul has already been completely consumed by Star Dream before this point, so it is not completely clear how Star Dream/Haltmann emits this noise. Star Dream could simply be using Haltmann's voice.
- This same death may be a reference to Marx Soul's demise, splitting in half, screaming in pain, and exploding.
- The molten meteoroids Star Dream and Star Dream Soul OS release from a portal are a reuse of the molten boulders seen in Dangerous Dinner and Pyribbit's boss fight.
- A number of Star Dream Soul OS's attacks - especially in its last phase - are references to attacks used by other final bosses, particularly Marx Soul (who notably also derived his power from a Galactic Nova):
- The void that Kirby can be dragged into is the same one used by Marx, Marx Soul, Magolor's third form, and Magolor Soul.
- The cutter attack used by the heart is a reference to the cutters used by Marx, Drawcia Soul, and Soul of Sectonia.
- The heart-splitting attack is a reference to the attack in which Marx Soul's body splits into blue and pink energy blasts.
- The heart of Star Dream Soul OS is fought in a room resembling the main office of the Access Ark. Susie describes the room in Access Ark as "the heart of the company." Considering the resemblance of the two areas and Susie's statement, it could be assumed she meant it literally.
- The third of the red shock waves the final phase blasts out when defeated is the most powerful attack (that does not instantly KO Kirby) a boss can use in Kirby: Planet Robobot, and possibly the entire series.
- In addition, this also makes Star Dream Soul OS the only boss in the entire series to use a last-resort attack.
- At the start of the first phase, Star Dream Soul OS appears to bleed just before the player gains control of the Halberd. This makes Star Dream Soul OS the fifth boss in the Kirby series to 'bleed', preceded by 0, 02, Shadow Dedede and Dark Meta Knight.
- Star Dream is a machine rather than an organic life form, so it is possible that the 'blood' is actually oil rather than organic blood.
- The cry that Star Dream Soul OS (and, by proxy, the original Star Dream) makes at the beginning of its third form includes audio of director Shinya Kumazaki's pet cat meowing. The sounds produced by the weathervanes in the battle against the third form include audio of real chickens. One member of the sound team keeps chickens at home and recorded them for the game.
- During the second half of the final phase, Star Dream Soul OS's heart will slowly rotate to face Kirby, if it is in the middle.
- During Star Dream Soul OS's first phase, it will occasionally flip sideways or upside down after teleporting, presumably to make it a more difficult target. Star Dream does not do this during the Main Mode of Kirby: Planet Robobot.
- Star Dream Soul OS is the only Soul boss that is not undead, as instead it is mechanical.
- Star Dream Soul OS is the second Soul boss to not be revived by a powerful item, the first being Drawcia Soul.