Seelkadoom the Hedgehog

“	Very well. Come! I'll carve upon your flesh just how hopeless the very thought of defeating me really is.	”
–Seelkadoom's threat to Shadow, Knuckles, and Nights, Episode 9

Seelkadoom being created — Seelkadoom Being Created

Seelkadoom the Hedgehog is a fusion clone of both Sonic and Shadow the Hedgehog. He is the main antagonist of Sonic RPG. He was created by Dr. Ivo Robotnik in his laboratory with the Chaos Emeralds, combining their negative chaos energy with the DNA of Sonic and Shadow. He is the completed work of Dr. Eggman's Grandfather, Gerald Robotnik.

Concept[]

Seelkadoom was originally inspired by the fusion of Sonic and Shadow, known as Shadic, who appeared in the 2004 Movie "The Power of Nazo". MidNightMaren then made a different design of a combination of Sonic and Shadow, with a more menacing look, confirming that he is basically Shadic, but an evil version.

Appearance[]

Seelkadoom is a black Hedgehog, with blue stripes all over his spikes, representing the stripes that Shadow has, and Sonic's fur color. He has his skin shown on his arms and belly, representing Sonic's body with it's color being tan, representing Shadow's skin color. He has a pair of sneakers that look like Sonic's, only they are colored dark gray instead.

Personality[]

Seelkadoom has the personality combined of Sonic and Shadow, only evil and more destructive. He also appears to have his own personality, likely because of his negative Chaos Energy side.

Like Sonic, he never misses an opportunity to mock and tease his opponents, even in a fight, representing Sonic's arrogance and irreverence but remaining threatening, showing in Episode 8 how Seelkadoom tells Sonic that "looks that light speed just isn't enough". He also appears to be very arrogant, insensitive and aggressive, very similar to Shadow, only much more violent, showing how he doesn't care much about his partner, Reala, and that he only uses him as a pawn, scolding him when he messed everything up, regarding their plans to take the Sapphire, as well as feeling no remorse for Reala's death in Episode 7, claiming that "his death was well deserved". It is also represented, where Seelkadoom claims himself as "the superior hedgehog", and therefore mostly toys with his counterparts in battle more than their other friends, NiGHTS and Knuckles, whom he knocks them out with a simple attack, showing disinterest in fighting them. Furthermore, after his birth, Eggman called him "Sonaw", which angered Seelkadoom, to which he changed it to his desired name, showing a strong sense of liberty just like Sonic, although he doesn't care when it happens to the other.

With his power, Seelkadoom is very independent, having no hesitation whatsoever to take control over the ones he teams up with and betraying them in the end, even his own creator Eggman. He also doesn't seem to be afraid of anything, even though his opponent is stronger than him, as when Sonic turned Hyper, Seelkadoom was very angry for a moment and then he mocked him stating that "this new trick of yours won't change your fate", and then fought him without hesitating. He is very intelligent and strategic as well, given the fact that he is a fused being, as he easily can spot weaknesses of his opponent very quickly, to win his fight (a good example of this is when Seelkadoom threw Shadow's confidence with force to the ground to make him act impulsively during episode 2), as well as secretly gathering and possessing the Emeralds all this time, without anyone noticing, right after his birth.

His cockiness however can also be a weakness to him, as that gives his opponents an opportunity to power up against him, and catch him off guard, as shown in Episode 9, how he let Sonic turn Hyper, instead of killing him and his friends right away.

Quotes[]

"Oh, Sonic. Why don't you just give up already?" - Seelkadoom to Super Sonic in Sonic RPG Ep5

"Ha Ha ha! As you wish... Brother!" - Seelkadoom before fighting Super Sonic in Sonic RPG Ep5

“Urgh… Sonic you will pay… You!… You will regret this…” - Seelkadoom slowly regaining consciousness from his battle with Super Sonic after his nightmare claiming he will have his revenge in Sonic RPG Ep6

“Time for a little surprise, Sonic!” - Before dashing away in Sonic RPG Ep7

"What an idiot. Did I not tell him to stay in the castle? His death was well deserved." - Not caring about Reala's death at the hands of Shadow and NiGHTS in Sonic RPG Ep7

“So long, little rodent” - Just when his about to finish off Shadow with a Dark Blast in Sonic RPG Ep7

“If you’re truly serious, then come and face me at Reala’s Castle! There we shall see the iron behind your words!” - Seelkadoom challenges Sonic to one last battle before flying away in Sonic RPG Ep7

"This suspense is simply awful. Come at me! Come, at Seelkadoom! Your doom awaits!" - At the start of the battle in Sonic RPG Ep8

"Come, and face oblivion..." - Using Wave of Oblivion/Arrogance

"Witness my power!" - Using Dark Blast/Ultimate Devastation/Lance of Time/Apex Swarm/During Ultimate Devastation

"Die!" - Using Dark Spear Rain/Seelkadoom after beating Super Sonic and Super Shadow in Sonic RPG 8

"This battle... IS OVER!" - After beating Seelkadoom in Sonic RPG Ep8/Before using Ultimate Devastation in Sonic RPG 9

"What's wrong now? Losing speed, Sonic?" - During the epilogue of Episode 8 against Super Sonic

"It seems that lightspeed just isn't enough.." - Before giving Super Sonic a barrage of hits in the epilogue of Episode 8

"You lot... you truly think you can make a difference?" - Seelkadoom against Shadow, NiGHTS and Knuckles in Sonic RPG Ep9

"Very well. Come! I'll carve upon your flesh just how hopeless the very thought of defeating me really is." - Seelkadoom's threat to Super Shadow, NiGHTS, and Knuckles in Sonic RPG Ep9

"Ha! Finally! No one left to oppose me!" - Seelkadoom defeating Super Shadow, NiGHTS, and Knuckles in Sonic RPG 9

"What?..." - Seelkadoom seeing Sonic getting up and becoming Super Sonic again in Sonic RPG 9

"How?! How can you be up again?! Where does that power come from?!" - Seelkadoom seeing Super Sonic getting up even after that beating from Sonic RPG 8 in Sonic RPG 9 - RPG 10

"What the hell is that?" - Seelkadoom seeing Sonic in his Hyper form.

"Huh. No matter... This new trick of yours won't change your fate." - Seelkadoom against Hyper Sonic in Sonic RPG Ep10: Act 1

"Hmph. My turn." - Seelkadoom prompting his turn in Act 1

"Are you finished?" - Seelkadoom readying Dark Blast in Episode 10

"So much bravado... for absolutely nothing." - Seelkadoom after beating Hyper Sonic in Act 1

"Your speed is truly astonishing... I'm impressed. But that speed means nothing, when your fists lack the power to faze me. Besides... that power of yours won't last much longer!" - Seelkadoom against Hyper Sonic in Act 2

"Ha! See? Even your speed begins to betray you! So much for being The Fastest Thing Alive..." - After surprising Hyper Sonic with his own superspeed and grazing his cheek while the Blue Blur was in his Hyper Form

"Die!" - Seelkadoom after beating Hyper Sonic in Act 2

"What is this?!" - Seelkadoom almost being defeating by Hyper Sonic

"You bastard..." - Seelkadoom after having his Chaos Spear deflected by Hyper Sonic in Act 3

"STOP. RUNNING FROM ME." - Before transforming into Apex Seelkadoom

"You... I'LL CRUSH ALL OF YOU." - After transforming

"Is that your best?" - As Apex Seelkadoom

"I'll make you regret saying that..." - Apex Seelkadoom using Wrath of the Apex

"Tch. You are nothing..." - Apex Seelkadoom using Prance of the Apex

"Hahaha! Is that all you've got?!" - Apex Seelkadoom using Bulwark of the Apex

"Face oblivion!" - Apex Seelkadoom using Monochrome

"What an idiot... his death was well deserved." - Apex Seelkadoom after beating Hyper Sonic in Act 3

"This dimension... shall be mine!" - Apex Seelkadoom after powering up against a weakened Hyper Sonic

"What are you doing, you bastard?!" - Apex Seelkadoom towards Knuckles as he felt his connection to the Chaos Emeralds slip away

"You...!" - Towards Hyper Sonic at the end of Act 3

"Hahahaha!" - Apex Seelkadoom after beating Hyper Sonic in the first QTE section of Act 4

"I'll crush all of you!" - Apex Seelkadoom in the final QTE section of Act 4

"DIEEEEEEEEEE!" - Full Power Apex Seelkadoom after beating Hyper Sonic in the final QTE of Act 4

Powers & Abilities[]

Seelkadoom is by far, the strongest in the series so far, being created with Sonic and Shadow's DNA and negative Chaos Energies of all 7 Chaos Emeralds, making him a very dangerous, durable, and strategic fighter. His durability is high enough, that he still puts up a good fight and displays amazing reflexes even when stunned by even the most devastating attacks, as well as surviving such attacks even when being at his weakest, though it may also depend on how much energy his opponent puts into his attack. Sonic stated, that even in Seelkadoom's weakened state, he still doesn't think that he could actually kill him. His strategicness is shown to be higher than Sonic, Shadow and co. in nearly all situations, shown in battle how Seelkadoom always finds out any weaknesses in his opponents to win his fight, however strong they are. Seelkadoom possesses all the powers and abilities of Sonic and Shadow, as well as his own abilities thanks to being made of dark chaos energy, such as absorbing energies of his opponents, other life forces, stars, or simply just any entire Universe, (allowing for him to increase his power further), as well as having the ability of flight already, despite not being in a transformed state, which is something that Sonic and Shadow can't do in their base forms. He is much more of a master Hand-to-hand combatant than his counterparts and Knuckles, and is also shown mimicking moves and powers from other fighters as well.

Being a combination of powerful users of Chaos Energy, and Chaos energy itself, Seelkadoom has a far greater connection to the Chaos Force than even Super forms do, displaying such monstrous power, already without the Chaos Emeralds, that he can stand up to and take down Super forms easily, however, at the cost of tiring out quickly in battle, which also depends on how much energy Seelkadoom uses up, due to him having left the Emeralds at Reala's Castle. That makes Seelkadoom already stronger than pretty much everyone in the Series, including Reala, (As Seelkadoom mentioned that he can kill him easily). That is shown in Episode 3 and 5 how Seelkadoom was easily able to fight well against Super Sonic and defeat him, before tiring out, which led to him being knocked out unconscious by Super Sonic. Realizing, that without the Emeralds, it wouldn't lead Seelkadoom to victory, Seelkadoom went to Reala's Castle to take them back for himself to increase his powers and already strong connection to the Chaos force, thereby eliminating the drawback of weakening, due to the Emerald's source of unlimited power.

Having done so, he could easily outmaneuver and outspeed both Super Sonic and Super Shadow combined, without even trying, nor using his full power, which forced Sonic to combine his Super form with the Sapphire's power, to transcend into the Hyper Form. Seelkadoom against Sonic's newfound strength, finally having unleashed his full power, could still hold his own against him for at least a bit, even landing at least a few blows on him but Sonic was rather unfazed and still had the complete upper hand against him, also being noted by Shadow. That in turn, forced Seelkadoom to finally utilising the dark power of the Emeralds to the maximum (possibly having drained half of their power), which turns him into his own Super transformation Apex Seelkadoom, amplifying his connection to the Chaos force yet even further. He can stay in this state without a time limit and has unlimited stamina.

In this state, Seelkadoom appears to have surpassed Hyper Sonic, having turned the tables on him once again in battle, to the point where Sonic was forced to come up with the strategy for Knuckles to utilise the Sapphire, to stop the Emeralds from keeping Seelkadoom empowered, as it's revealed, that it has the same properties as the Master Emerald. Before Seelkadoom could defeat Sonic once again, Knuckles began reciting the chant of the Master Emerald on the Sapphire, weakening Seelkadoom, to the point where Sonic could faze him, though Seelkadoom still put up a tough fight. After Knuckles successfully stopped the Emeralds on time, Seelkadoom (who returned to his weakest level), was defeated by Sonic's energy beam. It appears Seelkadoom has survived, but remained unconscious, though it may also have to do with Sonic wanting to spare Seelkadoom.

It seems that during the fight, Seelkadoom was holding back, toying with Sonic like he did previously. Before landing a final blow on Sonic, Seelkadoom seemingly powered up further, and in the final act of Episode 10, if the player fails to press all the keys, Seelkadoom uses the full power of his Apex form, turning him into a purely black being with blank white eyes. Having done so, he is able to easily overpower and defeat Hyper Sonic with just one hit of his energy beam, with no effort, which theoretically, could also mean that he can easily take on and defeat more than one fighter in Hyper form.

Seelkadoom actually was never defeated once in a battle, in terms of raw power, direct combat and strategy. If it weren't for Knuckles' help, along with Seelkadoom being distracted by the others, Seelkadoom would have won the fight.

Techniques[]

Episode 3:[]

Osmose - Seelkadoom absorbs power from his enemy.

Magical Apokaliz - Seelkadoom’s strongest attack. Using chaos control, Seelkadoom freezes time and constantly attacks his enemy. Afterwards, sending a powerful energy blast at them before creating two after images that attack his enemies before they’re absorbed into the enemy and deal even more damage.

Episode 5:[]

Dark Energy Beam - Seelkadoom can blast his enemy with a charged dark energy beam.

Aura Shield - Seelkadoom charges his power, increasing the range and size of his aura to act as a shield to block attacks with his dark chaos energy.

Episode 7:[]

Telekinesis/Psychokinesis - Seelkadoom can move items and objects around him with his mind.

Episode 8:[]

Chaos Control - Seelkadoom can teleport and control the flow of time.

Chaos Spear - Seelkadoom can generate golden bolts of chaos energy.

Dark Spear - Seelkadoom can generate black and blue Chaos Spears.

Dark Rush - Seelkadoom tackles his enemy, then blasts them with Dark Spears.

Dark Spear Rain - Seelkadoom releases Dark Spears in the sky and sends it raining down on his enemy.

Wave of Arrogance — Wave of Oblivion/Arrogance

Wave of Oblivion/Arrogance - Seelkadoom taunts his enemy into attacking him with his shield activated and sends a wave of Dark Spears out.

Dark Blast - Seelkadoom blasts the arena with highly compressed dark energy, heavily damaging anything within a 25 mile radius.

Episode 8 Game Over:[]

Execution Orb - Seelkadoom fires downwards lethal orb of dark chaos energy. This attack is normally used to finish off an opponent.

Episode 9:[]

Speed Strike - Seelkadoom teleports to a nearby foe and then attacks them at blistering speeds and finishes off with a small but strong blast of chaos energy from his hand.

Chaos Hazard - Seelkadoom charges his power and summons a magical drop of chaos energy which when it hits the ground, it forms a large purple terrain buzz saw-like object that damages anyone within its range.

Gleaming Cosmic Veil - Seelkadoom charges his power and summons a shining eclipse eventually emerging into a Aqua-Blue planet-like sphere that damages anything it comes into contact with.

Dark Gust – Seelkadoom performs a powerful blast of dark energy around himself when he’s overwhelmed blowing the opponent away.

Pillars of Pain - Seelkadoom charges his power and does three tall beams of energy hitting multiple targets.

Ultimate Devastation – (direct reference to Magical Apokaliz). Seelkadoom charges at his targets and then continuously attacks them at blinding speeds, then charges some chaos energy in himself then leaps upwards and then charges again some dark energy into his hand for a small but powerful shot at his targets. (Dark Shot).

Episode 10 Act 1:[]

My Turn! - Seelkadoom dashes at the opponent and does basic combo and then does a powerful side-kick sending his opponent flying away.

Skyward Splicer - Seelkadoom kicks his foe to the sky, does a barrage of kicks at them, delivers an eagle kick, and finishes with a backhand to knock them away.

Chaos Cannon - Seelkadoom unleashes an energy beam at his target.

Episode 10 Act 2:[]

Meet Your Maker - Seelkadoom charges at the opponent and does a strong back kick, then follows up with a Double Updraft Kick (similar to Sonic Updraft) to the ceiling and finishes it off with an Eagle Kick to the ground.

Bon Appétit - Seelkadoom unleashes a barrage of blows at his target, then fires a blast of purple Chaos Energy that detonates on impact.

Vanity - Seelkadoom unleashes a blue sphere of Chaos Energy that he fires at his target, that he is then prepared to deflect back at them if they try to redirect it at Seelkadoom.

Penumbra Moonsault - Seelkadoom sends his target to the air with a kick, and spindashes towards them at great speed from above, dealing immense damage.

Lance of Time - Seelkadoom strikes the opponent with a purple Chaos Spear-like projectile that stops time when hit, then performing several attacks afterwards.

Osmosian Onslaught - Seelkadoom does a barrage of combos, and unleashes his own variant of Sonic's Humming Top attack, then finishes it off with a spindash.

Episode 10 Act 3 - Apex Form Techniques:[]

Ferocious Prowl - Seelkadoom charges at the opponent and then stealthily hides in a shadow out of sight, fooling the opponent into thinking he’ll attack them head on. Once he’s behind his opponent without them knowing, he proceeds to do a slew of vicious attacks, finishing off with an a powerful downer-cut with both hands.

Wrath of the Apex - Seelkadoom boosts his own attack power, granting him a boost in offense.

Prance of the Apex - Seelkadoom boosts his own attack speed, allowing him to attack more frequently.

Bulwark of the Apex - Seelkadoom boosts his own defense, granting him more resistance in durability.

Vierstufige Symphonie - Seelkadoom does a slow, but punishing four-hit combo on his target, with the last hit being a brutal wind-up punch.

Apex Swarm - An upgraded variant of Dark Spear Rain that deals more damage and is much faster than the former. Seelkadoom does this attack by sending blue Chaos Spears raining down in a diagonal angle at his target after a slight charge.

Figures of Paranoia - Using afterimages to surround and distract his enemy, Seelkadoom takes this chance to unleash a devastating blast that causes a massive explosion, that knocks his target far away while dealing immense damage.

Desperado - Seelkadoom unleashes a barrage of attacks, followed with an attack that is his own variant of Shadow's Chaos Nightmare. He then finishes an attack with a brutal kick that causes a secondary after-hit upon first contact, knocking the target back.

Monochrome - Seelkadoom surrounds the world in a zone of negative energy, creating an extremely hostile environment that drains both the opponents energy and life force.

Apex Annihilation - Seelkadoom locks his foe in place, then collectively charges massive amounts of energy in his whole body that he then expels. Once done, he will rush towards his target and strike all around them at breakneck speeds, then finishes with one brutal punch.

Acts 1-3 Game Over Attacks:[]

Galactic Explosion - An upgraded variant of My Turn! and Dark Blast combined where after Hyper Sonic reverts back into his base form, Seelkadoom seizes his chance and kicks the blue hedgehog's face, sending him crashing towards the wall. He then grabs Sonic and takes him to the sky, amasses his powers and causes a massive blast around them, killing Sonic instantly. Seelkadoom then drops the blue hedgehog's lifeless body, smirking while berating Sonic's attempt of fighting him. This will be shown in the First Act of Episode 10 if the player fails the first battle against Seelkadoom.

Evisceration Blast Bomb - An upgraded variant of Meet Your Maker, Bon Appétit, and Penumbra Moonsault combined where Hyper Sonic reverts back into his base form and falls down towards the floor, hitting it two times before landing and getting up on his feet. That's when Seelkadoom sneaks up on him, kicks him up to the roof, and kicks him again, sending him to the wall, destroying and going through the wall in the process. The black-and-blue hedgehog then fires a huge purple Chaos projectile at his target, destroying him in an instant, then strikes a pose with a sinister smile and glare. This will be shown in the Second Act of Episode 10 if the player fails the second battle against Seelkadoom.

Apex Destroyer - An upgraded variant of Ferocious Prowl, Desperado and Vanity combined where after Hyper Sonic struggles to maintain his Hyper Form (flickering from base form to Hyper form in a split second), Apex Seelkadoom seizes the chance to strike Hyper Sonic with a spindash (and calling Hyper Sonic an idiot before doing so), followed up with a kick, and then unleashes a barrage of kicks leading to a somersault kick upwards. Apex Seelkadoom then rushes upwards and grabs Hyper Sonic by the face, sending him plummeting down while charging up an energy ball in his hand while he held a firm grip on Hyper Sonic's face. As he fires the blast, Hyper Sonic is reverted to base form and is sent down from the skies, with a massive explosion of Chaos Energy occurring afterwards- with a rather unamused Apex Seelkadoom looking away from the blast and facing the screen stating that Hyper Sonic's death was well-deserved. This will be shown in the Third Act of Episode 10 if the player fails the third battle against Apex Seelkadoom.

Episode 10 Final Act:[]

Apex Rush - An upgraded variant of Dark Rush where Apex Seelkadoom rushes at his target while being engulfed in his own aura of black and blue Chaos Energy. This will be shown in the Final Act of Episode 10, if the player fails the first QTE section.

Oblivion Orb -Apex Seelkadoom amasses his Chaos Energy to his hand forming a black orb with turquoise outlines and electricity, which is powerful enough to force his target out of their transformations once fired at them. This will be shown in the Final Act of Episode 10, if the player fails the second QTE section.

Midnight Cannon - Apex Seelkadoom fires a massive dark beam, clashing against an Azure Blast fired by Hyper Sonic. Apex Seelkadoom after a brief power struggle become crazed and uses the seven Chaos Emeralds to unleash the full might of his Apex form, and fires an upgraded version of Chaos Cannon to overpower Hyper Sonic's Azure Blast effortlessly. This will be shown in the Final Act of Episode 10, if the player fails the final QTE section.

Transformations[]

SonicRPG Seelkadoom Transformation — Apex Seelkadoom in the Sonic RPG 10 Trailer

Apex Seelkadoom: Due to having the DNA of Sonic and Shadow, Seelkadoom has access to the super transformation, after powering up with the 7 Chaos Emeralds, albeit with negative chaos energy, which turns his form into a different color, instead of gold. Besides his quills being curved upwards, his eyes and fur instead, turn into a dark royal navy-blue color, his stripes and shoes turn jet-black and fur has grown on his arms and belly. In this form, he surpasses Hyper Sonic - even though Sonic was able to keep up against him, albeit barely. According to MidNightMaren, Apex Seelkadoom is stronger than Hyper Sonic, but still slower than him.

Full power Apex Seelkadoom(Midnight Cannon) — Full Power Apex Seelkadoom fires Midnight Cannon

Full Power Apex Seelkadoom: Apex Seelkadoom uses seven chaos emerald powers up his Apex form to it's fully maximum power after pretending to being holding back and crazed, resulting in his entire body being completely consumed in black Chaos Energy and his eyes turning completely white with no iris or pupils present. This boost in power was so powerful that Apex Seelkadoom can fire unlimited Midnight Cannon to overpower Hyper Sonic's Azure Blast with his own effortlessly. This will be shown in the Final Act of Episode 10, if the player fails the final QTE section. It is possible that in the cutscenes, Apex Seelkadoom was indeed holding back, meaning if he actually would have gone all out, he would have turned into that state, where not only could he get rid of Hyper Sonic with just one hit, but could also have no problem taking on and easily defeating at least 2 or more fighters in Hyper form combined, hypothetically speaking.

Supreme Seelkadoom: Due to having the DNA of Sonic and Shadow, Seelkadoom technically has access to the hyper form as well, should he gain possession of all 7 Super Emeralds (or possibly the Sapphire). However, this was not seen in the series and is just a hypothetical situation, leaving it unknown how Seelkadoom would look like and be called in this form. His Hyper form is referred to as ''Supreme Seelkadoom'' by fans. He could have gone hyper in the series. Since he already had the Super form, Apex Seelkadoom, and he was already stronger than Hyper Sonic, he could have taken the latter's Sapphire and use it's power for his Super form. That would cause Apex Seelkadoom to become Supreme Seelkadoom.

Trivia[]

Initially, it was unknown, why Seelkadoom was overpowered by Super Sonic in Episode 5. Fans argued, that Seelkadoom was trying to fool Sonic, by holding back and was too cocky, that Sonic somehow caught him off guard and knocked him out unconscious. Others said Seelkadoom left the emeralds in Reala's Castle. It was later confirmed by MidNightMaren, that the second one is what actually happened, explaining the power inconsistencies and why Seelkadoom was weakening. Seelkadoom most likely wanted to test how strong he is without the emeralds.
Also another very uncommon theory of Seelkadoom's weakness was that due to being half Shadow and having surpassed his level of chaos manipulation, without support of the Inhibitor Rings like Shadow, Seelkadoom will indefinitely drain way more energy than necessary leading to burnout and extreme exhaustion. Meaning the only way to eliminate this drawback is to take advantage of the limitless supply of energy from the Chaos Emeralds.
It is unknown why Seelkadoom seems to target Sonic more than Shadow, despite being part Shadow. It can be assumed that the machine Seelkadoom was born in programmed him that way, considering that Eggman wants Sonic's death more than Shadow's death.
Due to Shadow having the blood of Black Doom, Seelkadoom is, by technicality: the son of Black Doom.
His Apex form is extremely similar to Dark Sonic from Sonic X and Sonic: Nazo Unleashed. Both share more or less identical appearances, the same auras and are both powered by the negative power of the Chaos Emeralds. This makes the Apex form as Seelkadoom's own version of the Dark form. It is even possible, that it was inspired by and modeled after Dark Sonic.
- Furthermore it should be noted that the Dark form is the Super transformation, but with dark chaos energy.
It is unknown what happened to Seelkadoom after the events of the Series. It is possible, that he either was killed offscreen by Eggman or the heroes with the help of the emeralds, or Seelkadoom has successfully stolen the Emeralds once again, this time with the Master emerald for a possible rematch against the heroes. Though whether Seelkadoom can use the Emerald's power again is still up for debate, as Knuckles commanded the Sapphire to "stop that beast from using the Emeralds's power any longer". The fate of Seelkadoom is unknown.
One of his attacks in the 3rd Act's Phase 3 is somewhat similar (or inspired by) Akuma's signature Shun Goku Satsu attack, where he delivers swift blows that would end up as the killing blow, as well. In Seelkadoom's case, he locks Hyper Sonic in place, then collectively charges massive amounts of energy in his whole body that he then expels. Once done, he rushes at Hyper Sonic and strike all around him at breakneck speeds, then finishes the attack with one brutal punch.
The Wave of Oblivion attack was given an official attack name, called "Arrogance". This was confirmed by the Official Sonic RPG Twitter, stating it was directly from Raynor Foxhound himself, who is Seelkadoom's voice actor in the game.
The game over animation that plays in the third and final QTE section of Act 4 is a reference to the final moments of Nazo Unleashed, where Hyper Shadic unleashes the full power of the Super Emeralds to turn into a purely white being, and defeats Nazo in one powerful blast without any effort exerted. In Seelkadoom's case, he uses the full extent of the Chaos Emeralds to unleash the full power of his Apex Form, turning himself into a purely black entity with white glowing eyes, and effortlessly overpower Hyper Sonic's Azure Blast with an empowered Midnight Cannon.
According to MidNightMaren, Seelkadoom doesn't use negative energy, contrary to popular belief.