Alien X

Alien X is the Omnitrix's DNA sample of a Celestialsapien from the Forge of Creation.

Appearance
Alien X is a humanoid alien that is all black excluding his hands, which are white. He has tiny white star-like spots all over his body. His eyes are green with no pupils. On his head are 3 horns like Ultimate Way Big.

In Omniverse, Alien X retains his original appearance, but his chin is now bigger, like Diamondhead's. He is more muscular and his horns are smaller. The stars on his body are now brighter.

Alien X wears the Omnitrix/Ultimatrix symbol on his chest.

Backstory
Ben acknowledges Alien X as his most powerful alien; however, he cannot afford the cost that comes with transforming into Alien X.

Alien X has three personalities: Serena, the voice of love and compassion, Bellicus, the voice of rage and aggression and Ben, the voice of reason. All three speak in unison when Alien X speaks.

As Serena and Bellicus have been arguing for eternity and before they had no tiebreaker, getting them to focus on any present task is difficult at best, leaving Alien X's body trapped in place until an agreement is made.

However, in Omniverse, Ben uses Alien X successfully to create a near exact copy of the universe when it gets destroyed by the Anihilaarg.

Powers and Abilities
Alien X is omnipotent, being able to warp reality, time, and space to any level he wishes.

Alien X's reality warping is so powerful, that even his mere thoughts can become real.

Alien X can create time waves to reverse anything as seen in X = Ben + 2.

Alien X can create an entire universe at will, as seen in So Long, And Thanks For All The Smoothies.

While the Anihilaarg was destroying the universe, Alien X was unharmed.

Weaknesses
In order for Alien X to perform any action, including simple movement and transforming back, at least two of his personalities must agree to do so. This has proven to be a major weakness, as Serena and Bellicus weren't interested in dealing with present affairs and wanted to finish past ones that weren't possible to deal with without Ben.

In Ben 10,000 Returns, the said weakness was referenced by Paradox, where he revealed that there is an alternate timeline where Albedo transformed into Negative Alien X and was stuck motionless for nearly a year.

Alien X is vulnerable to having his powers absorbed, as Ben and Azmuth have implied that Darkstar and Osmosians can absorb his omnipotent powers.

Ben 10: Alien Force

 * Alien X first appears in X = Ben + 2,
 * Alien X stops a flood caused by a broken dam. After much fruitless argument, Ben convinces Serena and Bellicus to transform him into another alien (mostly by insulting them).
 * Ben swears that he won't use Alien X again, as it is not worth the price.

Ben 10: Ultimate Alien

 * Alien X returned to Ultimate Alien in The Forge of Creation,
 * Ben half heartedly turned into Alien X in hopes of locating the Forge of Creation in his last-ditch effort to stop Ultimate Aggregor from obtaining the universe's greatest power. After transforming, Bellicus and Serena start debating about other things as usual. Suddenly Paradox appears, telling Ben that he would not be able to convince Bellicus and Serena to help him out today. Also, Paradox puts himself in danger by going into the presence of Bellicus and Serena who almost voted to destroy him, and changes Ben back into his human form before they could come to a vote.
 * In Ben 10,000 Returns, Alien X was mentioned by Paradox, where in an alternate timeline, Albedo turned into Alien X and was trapped motionless for nearly a year.
 * In The Ultimate Enemy: Part 2, Alien X appeared in the flashback.

Ben 10: Omniverse

 * Alien X returns to Omniverse in So Long, And Thanks For All The Smoothies,
 * Alien X successfully recreates the universe (albeit not being an exact duplicate).
 * in Universe Vs. Tennyson,
 * Alien X defeated the Galactic Gladiator.

Ben 10: Alien Force

 * X = Ben + 2 (first appearance)

Ben 10: Ultimate Alien

 * The Forge of Creation (first re-appearance)
 * The Ultimate Enemy: Part 2 (flashback, cameo)

Ben 10: Omniverse

 * So Long, And Thanks For All The Smoothies (first re-appearance)
 * Universe Vs. Tennyson

Video Games

 * Ben 10 Alien Force: Vilgax Attacks (alternate timeline)

Ben 10: Alien Force

 * 4" Alien X
 * Alien X (Planetary Powder)
 * Alien X (Alien Creatures set)
 * 10 cm Alien X (DNA Alien)
 * Alien X with Goop (Black version) (Creation Transporter)
 * Alien X (Defender) with Alien Bust
 * Alien X (Alien Creation Launchers)
 * Omnitrix Hero Collection with Alien X hologram
 * Alien X (Alien Rocks)
 * Alien X (Keychain)
 * Alien X (Deluxe)

Ben 10: Ultimate Alien

 * Alien Creation Alien X and Ben
 * Alien X Defender and Vulkanus (DVD and 4 inch action figures)
 * Classic Wildmutt, Nanomech, Spidermonkey Defender and Alien X (Combo pack)

Ben 10 Alien Force: Vilgax Attacks

 * Alien X appeared in the game (only in the CGI movies/clips for Xbox 360, Wii, PS2 and PSP). He is not a playable alien, being replaced by Cannonbolt/Murk Upchuck.

Online Games

 * Ben 10 Alien Force: Alien Attack
 * FusionFall (Nano)

Etymology
His name, made up of "Alien", a reference to being an extra-terrestrial life form, and a transformation, and "X", the roman numeral for 10, and referring to his mysteriousness.

In The Forge of Creation, the Ultimatrix referred to him as "Transformation 10", which still literally meant "Alien X", per above.

Trivia

 * Before Alien X appeared, the opening of Ben 10: Alien Force showed only a silhouette of him, after he appeared, it showed his full picture.
 * Alien X is a Nano and a former NPC in the game FusionFall.
 * The X in Alien X is actually referring to the Roman numeral of 10.
 * Alien X is named like this because he is the 10th alien in the recalibrated Omnitrix.
 * In Project Exonaut, Alien X is a level 10 suit.
 * In Andreas’ Fault, a fan of Ben refers to the Alien X smoothie as a disappointment as well saying it tastes like "filler." This is a reference to Alien X's constant standing in the series.
 * Ironically, in many promotional images of him, Alien X is posing dramatically (like in the openings to Alien Force and Ultimate Alien), while in the actual series, most of the time, he is frozen in a standing-up position.
 * In A Jolt From The Past, Rook speaks of Alien X, but believes he is just a rumor. Ben tries to convince him that Alien X is real, but Rook doesn't believe him and asks Ben to transform and show him, which Ben refused.
 * In So Long, And Thanks For All The Smoothies, Ben transforms into Alien X in front of Rook, causing him to realize Alien X is real.
 * Unlike most of Ben's aliens, Alien X has 4 fingers and a thumb.
 * Alien X's chin in Omniverse gives him a resemblance to the superheroes The Tick and The Crimson Chin.
 * Alien X was the first alien in Alien Force to not be voiced by Dee Bradley Baker. The second was Rath, who is voiced by John DiMaggio.