In his human form, Aptom appears to be a muscular Caucasian man with slick black hair and a distinctive scar running down the left side of his face. The scar is apparently a side-effect of his initial optimization procedure and is always present when he reverts to human form. He usually wears sunglasses in human form.
First appearanceAptom first appeared on the scene shortly after the destruction of Cronos' Japanese branch, along with his Lost Number compatriots Somlum and Dyme. The three of them were called in from Relic's Point to assist with the capture or destruction of Sho Fukamachi (Guyver-I). When Cronos commenced their plan to abduct Sho's father Fumio and his friends the Segawa siblings, the Lost Number commandos engaged Sho in battle and Aptom transformed into his battle form: an imitation of the Guyver. Aptom's abilities couldn't compare to the power of a real Guyver and he was grievously wounded during his first battle while Somlum and Dyme were killed. Consumed with rage, Aptom vowed revenge against Sho before retreating.
After Aptom's first defeat at the hands of Guyver-I, Dr. Barcas had Aptom re-optimized and enhanced with greater powers. The experiments resulted in Aptom being able to imitate any form and also allowed him to assimilate the cells of other Zoanoids, gaining their forms and abilities. More frightening still, Aptom could completely absorb Zoanoid bodies to make himself stronger and regenerate absolutely any wounds. He had gained total control over his individual cells as well, meaning that as long as even the tiniest scrap of his body remained, he would still be alive and could regenerate his form by assimilating other Zoanoids. Unfortunately for Cronos, however, an unforeseen side effect of Dr. Barcas' excessive experimentation also rendered Aptom immune to Zoalord telepathy, so he could not control him.With his newfound abilities, Aptom was sent out to spy on the Guyvers and their allies, who were hiding in the forests surrounding Mount Minakami. At this time, Sho Fukamachi had lost the ability to bio-boost after the trauma of killing his own father, who had been turned into Enzyme II, had caused him to surpress his memory. At one point, Sho and Mizuki Segawa would become seperated from the group and Aptom took the opportunity to strike at Sho, intending to make him suffer before he finally killed him. He disguised himself as Guyver-III in order to get close to Sho and even killed a squad of Zoanoids that were about to capture him and Mizuki. After saving the pair, Aptom dropped his disguise and revealed his human form then took Mizuki hostage. He then tormented Sho by reminding him of the truth behind his father's death and took on the form of Enzyme II in order to urge Sho into becoming the Guyver again, threatening to kill Mizuki if he couldn't. Sho was able to muster the courage and strength to transform once more into the Guyver and saved Mizuki before luring Aptom into the forest. Aptom revealed his new powers to Sho, how he could mimic other Zoanoid forms and even combine different zoaforms to produce new composite shapes with a variety of powers. Sho struggled to fend off Aptom's assault, but the Lost Number was able to instantly heal any damage Sho inflicted on him. Aptom used an Enzyme discharge to dissolve Sho's arms, preventing from opening his chestplate to fire the Mega-Smasher. However, using all his concentration, Sho willed his chest armour open without his arms. Aptom tried to annihilate Sho with a pair of enhanced Vamore bio-lasers, but the Guyver fired the Mega-Smasher at the last moment, engulfing Aptom's own beam and blasting the monster away. Sho believed Aptom to be dead and walked away to find Mizuki, leaving behind nothing but Aptom's severed arm.
Although his body had been vaporised by the Guyver's Mega-Smasher, Aptom was able to partially regenerate from his severed arm. He vowed to hunt down Sho again, but first he needed to regain his strength. Luckily for him, Dr. Barcas had sent out the Hyper-Zoanoid Team Five to investigate the site of the recent battle between Guyver-I and an "unknown Zoanoid". Aptom camouflaged himself and waited for Team Five to draw near, then pounced on Elegen and began to absorb him slowly. While consuming Elegen, Aptom used Elegen's psychic link to Dr. Barcas to warn the doctor that he was coming after him to take revenge for all of the suffering he had endured as a Zoanoid test subject. He then completely devoured Elegen, gaining his powers, and threatened to come after Gaster next.
Aptom made his way back to Mount Minakami, carefully evading many of the Cronos troopers patrolling the surrounding area and consuming some of them as well. His progress was impeded by the sudden appearance of Archanfel, Cronos' founder and ruler. Thinking that Archanfel was another Zoanoid, Aptom lunged at him, but then realised his error. Archanfel unleashed an energy wave that almost completely destroyed Aptom, but his head survived and he later healed himself after consuming more Zoanoids.
Aptom eventually made it inside Relic's Point, intent on consuming the rest of the Hyper-Zoanoid Team Five. He had even managed to clone himself by invading the bodies of other Cronos guards and used these extra bodies to decieve Team Five as they attempted to deal with the deteriorating situation inside the base, which was being heavily damaged while Archanfel was battling traitorous Zoalord Richard Guyot. Team Five split up, with ZX-Tole and Derzerb moving out to rendezvous with Dr. Barcas while Gaster remained behind in an observation post. The Cronos trooper stationed in the monitor room was actually Aptom and he attacked Gaster while his back was turned, consuming him.
Another of Aptom's copies attacked ZX-Tole and Derzerb in a corridor, but the two managed to destroy the clone before it could invade either of their bodies. However, the clone that had assimilated Gaster then approached, wearing Gaster's form. Before ZX-Tole and Derzerb realised what was wrong, Aptom grabbed Derzerb's arm and began to invade the Hyper-Zoanoid's cells. ZX-Tole unleashed a volley of bio-laser blasts that obliterated Aptom's body, but it was too late: the cells Aptom had passed on to Derzerb took over and consumed him from within. Combining the genetic codes of Derzerb, Gaster and Elegen, Aptom created a new composite form that utilized the powers of all three Hyper-Zoanoids: Gaster's bio-missiles and liquid-explosives, Elegen's electrical whips and Derzerb's ultra-dense musculature and heat discharge.
Aptom taunted ZX-Tole and told him how he had duplicated himself, but didn't mention just how many clones he had made. With ZX-Tole the only member of Team Five left standing, Aptom had singled him out and promised to devour him next before unleashing a spread of bio-missiles. ZX-Tole was badly wounded by Aptom's attack but managed to continue fighting, counter-attacking by using his wings to absorb the light and heat from the surrounding area to charge his ultimate weapon, the Blaster Tempest. The Blaster Tempest destroyed three quarters of Aptom's body, leaving only his head and one arm dangling from a scrap of damaged concrete over the deep, dark chasm running down the centre of the Relic's Point base. With Aptom at the end of his rope, ZX-Tole moved in for the kill and prepared to destroy Aptom with his wrist-mounted blaster. But Aptom wasn't finished yet: he had a third clone lurking in the shadows that sprung its attack as ZX-Tole was about to fire. As the Aptom clone began assimilating ZX-Tole's leg, ZX-Tole blasted his own leg off and burrowed into the floor in order to escape.
Aptom may have failed to consume ZX-Tole completely, but be was still able to gain all his powers by absorbing the severed leg. The two Aptoms then fused into one, combining their collected genetic data into a greater whole. Shortly after the battle with ZX-Tole, Aptom was forced to abandon Relic's Point as the fighting in its lowest levels continued to shake the base apart. Also, the Creator relic - which the base was named in honour of - had been activated by the Guyvers and was lifting off, which would destroy the base and Mt. Minakami above. Aptom made his retreat and went into hiding for the following year.
After X-DayAptom ventured far from the Minakami area and arrived in Tokyo, where his enemies were also present. Cronos now controlled the city after initiating their plan to take over the world and Zoanoids were soon commonplace among the general public. With his immunity to the Zoalords' telepathy, Aptom was able to roam freely without Cronos becoming aware of his presence, though they undoubtedly suspected he was still alive.
A year after X-Day, Sho Fukamachi's allies were in hiding in Tokyo, taking cover in the house of one of the Segawas' schoolfriends, Natsuki Taga. Aptom had discovered their hiding place but made no attempt to interfere with them. He believed that one day, Sho Fukamachi - who had been missing since the destruction of Relic's Point - would return to protect his friends. Still eager for a rematch with the Guyver, Aptom decided to watch over Sho's friends until he returned. One day, however, Mizuki Segawa had tried to return to her family's home since her parents had no idea she was still alive. She was spotted by two inspectors from the Cronos Regulation Bureau and they recognised her from wanted posters that had been put up all across the city. Natsuki had gone out to find Mizuki and took her home and as the inspectors began following them, Aptom ambushed the two Zoanoid inspectors and consumed them. Doing so, however, had alerted Cronos to Aptom's presence in the city and Dr. Barcas had a surprise in store for him should he ever re-surface.
A day later, Aptom was approached in Shinjuku by ZX-Tole, who had been re-optimized by Dr. Barcas and transformed into a Lost Number: Neo ZX-Tole. Both Lost Numbers fought in the skies above the city, but ZX-Tole had been enhanced with the abilities of his former Team Five comrades and his body had been infused with a specialised virus that would prevent Aptom from invading his cells. The battle was ferocious and the city suffered considerable damage, with Aptom almost being killed. He only survived when Sho Fukamachi - ressurrected as the Guyver Gigantic - appeared and used his new powers to finally destroy ZX-Tole. Weakened from the battle, Aptom had to consume a nearby Zoanoid that was monitoring the whole event in order to regenerate and escape. Now that Sho had returned, Aptom promised he would be back to settle the score once and for all.
Alliance with the Guyver
Although Aptom had previously vowed revenge against Sho, he would find himself conflicted and questioning himself over whether his vengeance would have any meaning. As time went on, he would continue assaulting Cronos operatives and consuming Zoanoids, ultimately helping Sho and his friends in their efforts to undermine Cronos' rule, though not intentionally. After the reappearance of Masaki Murakami, who was now under the control of Archanfel, Aptom made the conscious decision to help Sho fight his former friend. While he hardly considered Sho a friend, he had previously protected the Segawas and Onumas before Sho had returned, finding some sense of purpose in that. Ultimately, Aptom would decide that it was Cronos who truly deserved his wrath as they were the ones responsible for all the suffering that he and his Lost Number comrades had endured, and so he continued to assist Sho and his allies in defying Cronos.
With the many abilities he had obtained by absorbing the Hyper-Zoanoid Team Five and other Zoanoids, Aptom was truly a force to be reckoned with. However, Cronos would develop their own means of countering him, including the development of the Enzyme III which was immune to Aptom's cell invasions and also Cabraal Khan implanting his own Zoalord cells into Aptom through a Zoanoid intermediary, allowing him to temporarily seize control of Aptom.
Aptom was originally intended to be able to morph into any Zoanoid, but the facsimiles he turned into lacked the strength of the originals. After he was re-optimized by Dr. Barcas, he became able to sample the genetic codes of any Zoanoid that he made physical contact with (this also worked with the Guyvers). He also gained the ability to rapidly regenerate any damage inflicted and morph into composite forms composed of the traits and abilities of multiple Zoanoids. His different forms are listed below.
- Lost Number - In his original Lost Number state, Aptom challenged Guyver-I by morphing into a facsimile of the Guyver itself. It was visibly different from the genuine article, possessing a circular maw filled with fangs and had none of the metallic parts normally present on a Guyver, such as the control medal. Aptom attempted to copy the Guyver's head beam and high-frequency arm blades, but Sho was able to slice through Aptom's blade with his own easily.
- Composite Form 1 - In his second battle against the Guyver, Aptom created a composite battle body that merged the strength and shock-absorbant skin of Gregole, the lasers from Vamore, and the corrosive blood of Enzyme II. Sho was able to defeat this form with the Mega-Smasher, but was unaware that Aptom was capable of regenerating from even the smallest portion of his body.
- Composite Form 2 - Aptom produced this form by combining the genes of three of the Hyper-Zoanoid Team Five: Elegen, Gaster and Derzerb. In this form, Aptom possessed the impenetrable skin and heat absorption/discharge abilities of Derzerb, the electrical whips and iono-charge levitation powers of Elegen, and Gaster's liquid explosives and bio-missiles. Aptom fought ZX-Tole in this form and was almost destroyed by ZX-Tole's Blaster Tempest, but part of his body survived and one of his duplicates managed to partially assimilate ZX-Tole, allowing Aptom to gain yet another power.
- Composite Form III - This form combines the attributes of every Team Five member (except for Thancrus since he was killed by Guyver-III long before Aptom was re-optimized). This form is more slender than the previous form and sacrifices Derzerb's hyper-dense musculature in exchange for ZX-Tole's impervious carapace, wings and multiple bio-blasters. He can also produce and launch a greater number of bio-missiles and can use Elegen's and ZX-Tole's combined energies to produce barriers to deflect incoming attacks.
- Chaos Mode - This is by far Aptom's most horrific and, at the same time, ridiculous form. It appears to be an amalgamation of random Zoanoid body parts hastily mish-mashed together into a single body. This form is the result of Aptom assimilating the Hyper-Zoanoid Gastal, who had been implanted with genes taken from the Zoalord Cabraal Khan. Khan had intentionally sacrificed Gastal to Aptom, hoping that Aptom would consume the DNA of a Zoalord and then become vulnerable once more to Zoalord telepathy. However, Khan did not fully understand how Aptom's body worked at the time and so his attempt to control him failed.
- Evil Form - This form occurs when Zoalord Cabraal Khan figured out Aptom's unique genetic structure and assumed full control over him. Cabraal powered up Aptom, due to his belief that Guyver-I and Bio-Freezer weren't able to free him from his control. This Aptom had many new weapons such as the Molecular Accelerator, a weapon that accelerate the molecular motion of its targets to cause a form of disintegration; the High Frequency Vibration Lancer, the ability to turn invisible and electric shocks emited from its three horns on the left side of the head. The Molecular Accelerator was shown to be costly as the user was left vulnerable in the moment of the blast because the user must be in a concentrated state; in this form, the user can fire it from its right side only. Partly due to his absorption of so many Zoanoids by this point, and to Aptom being controlled by Cabraal, his appearance is haphazard and "mishmashed", with very little symmetry.
- OmegaBlast Mode - This is Aptom's most up-to-date form. He looks to have the characteristics of his third composite form mixed with Bio-Freezer and a few other Zoanoids. He has the ability of Bio-Freezer, Stealth ability, Molecular Accelerator and High Frequency Lancer.