Alien X in his first appearance rewound time. Serena also tells Ben that Alien X can control the very nature of Time and Space.
Alien X has casually tanked the destruction of the Universe caused by the Annihilargh.
Alien X has created a duplicate Universe from scratch in almost exact detail. Ben messed up the taste of one of his favorite smoothies and completely changed how the sign looks.
Skurd uses Alien X’s DNA to create a sword and easily cuts through an extra-dimensional barrier meant to protect the Contumelia from the release of energy by the Annihilargh.
Celestialsapiens are confirmed to be the reason the voices of characters and the art style changed throughout the franchise. It was only brought up for the Universe though, because that was what the trial was about, but it is already known that voices of characters and the art style of the entire Omniverse was changed. Like the robots from Dimension 12, the entire Null Void, all of Ledgerdomain, the Alternate Timelines of the Ben Prime Universe, and etc. This has happened at least 3 times that we know of as well.
Alien X scales above a device called the Chrono Navigator created by Professor Paradox, this device was said to be able to destroy the entire Omniverse if misused, as we seen in one episode happening. Professor Paradox (who is the most reliable source of info on the show) constantly refers to the Celestialsapiens as “Omnipotent” and how powerful they are saying they have the Greatest Power throughout the franchise, knowing he has this handy dandy device on him at all times. So this is why Alien X scales above it.
Celestialsapiens were confirmed to be above and not affected by a device called the Chronosapien Time Bomb, that was able to erase all the Alternate Timelines in Ben 10 that contained a Ben or an Omnitrix, the one seen was designated to keep the Timeline it was in safe (which was the No Watch Timeline) along with keeping Vilgax safe.
Alien X defeats a gladiator of his species, named Galactic Gladiator. During the fight he creates many duplicates of himself, as well as a galaxy-sized black hole.
The Cosmos of Ben 10 is big and it is referred to as the Omniverse (not an Omniverse that supposedly contains all of fiction). This Omniverse was also mapped by Professor Paradox, and it is a complete map of Space-Time that extends through 17 Dimensions (in the Spatial and Temporal sense), the map is called the Map of Infinity.
(Ben 10: Ultimate Alien, Season 1 Episode 11)
There are infinite Universes as mentioned by Doctor Holiday, since Ben 10 follows Quantum Mechanics and String Theory, except it is a little different to our real world. These Universes are all different from one another and usually don’t have many similarities, like Ben not existing in Rex’s Universe or the entirety of the Null Void.
(Generator Rex, Season 3 Episode 11)
All of these Universes are a part of separate Timeline Multiverses, which every Universe is the Prime Universe that have points in time that are Main Timelines, which have an infinite amount of Alternate Timelines branched off of them, as stated by Professor Paradox and Matruant. These Alternate Timelines are referred to as Cross-Time and all of them are every bit as real as the Main Timeline, meaning that even if the Main Timeline is destroyed, they will still exist as they are connected, but don’t rely on one another. An example of this would be No Watch Ben’s Timeline still existing despite the Chronosapien Time Bomb destroying all the other Alternate Timelines that are a part of the Ben 10 Timeline Multiverse. The bomb was programmed not to touch the No Watch Ben’s Timeline, but that wouldn’t work if the Alternate Timelines relied on the Main Timeline to exist, which was destroyed during that event or rather erased out of existence.
(Ben 10: Ultimate Alien, Season 2 Episode 10)
(Ben 10: Omniverse, Season 7 Episode 9)
(Ben 10: Omniverse, Season 6 Episode 1)
Speaking of the Ben 10 Timeline Multiverse, this is the main one we see in the franchise, and it started when Ben Prime received the Prototype Omnitrix, which to remind everyone this is only one point in time that became a Main Timeline of that Prime Universe. This is the reason why Professor Paradox and No Watch Ben were able to reboot the Ben 10 Timelines, as they went to the Universe before Ben Prime received the Omnitrix. Proof of the other Universes having Alternate Timelines, would be when we see Eon (an Alternate Ben) in the Null Void that looks like it is linear to his Timeline that is a part of the Ben 10 Timeline Multiverse. There is also the fact that we would have seen multiple Bens, Gwens, Kevins, Charmcasters, and etc. in Ledgerdomain if the other Universes didn’t have Timelines that branched off them.
(Ben 10: Omniverse, Season 6 Episode 1)
(Ben 10: Omniverse, Season 6 Episode 2)
(Ben 10: Omniverse, Season 6 Episode 2)
(Ben 10: Omniverse, Season 2 Episode 8)
(Ben 10: Ultimate Alien, Season 1 Episode 14) (Don’t really need to watch this, just an example)
There are also 26 Spatio-Temporal Dimensions (that matter), but the show never really elaborates on these. We never really see any of these Spatio-Temporal Dimensions within the series, but we have seen some of these Higher-Dimensional beings, which are the Naljians and Contumelia. We have no clue how big the Spatio-Temporal Dimensions are or how much more powerful a Spatio-Temporal Dimension is than each other (other than speculation).
https://gfycat.com/briskmisguideddwarfmongoose
The gif is like this, so people can hear the statement, but if you’d rather read it here it is. (Make sure to click unmute, if you watch it)
Naljian Mother: It’s just that you are such a young species. You only perceive three dimensions. Is that right?
Ben: Yeah. How many are there?
Naljian Mother: Only 26 that matter. You’ll work it out soon, I’m sure.
Ben: Uh-huh.
Naljian Mother: My point is that this “dangerous weapon” you fear is nothing more than my daughter’s favorite toy.
Kevin: Get out of town.
Naljian Mother: We were on an afternoon excursion to the lower dimensions, and she must have dropped it out of her carriage.
(Ben 10: Alien Force, Season 3 Episode 12)
Finally, there is the Forge of Creation, this is the home to Alien X’s species, the Celestialsapiens. The Forge of Creation exists outside of the Universes and when Professor Paradox spoke of it he said it is the source of the Universe’s greatest power and is where ideas become real, Azmuth also speaks about it being the greatest power in the Universe (though it doesn’t exist in the Universe). Professor Paradox also hid the Forge of Creation and enclosed it in something called the Chrono Randomization Barrier, which is out of sync with all Time and makes it inaccessible to anyone who doesn’t have the Map of Infinity, of course unless you are Professor Paradox or a Celestialsapien.
(Ben 10: Ultimate Alien, Season 1 Episode 16)
(Ben 10: Ultimate Alien, Season 1 Episode 16)
(Ben 10: Ultimate Alien, Season 1 Episode 16)
I have also made a map of my own recently, it is no Map of Infinity, but it should give a general idea of the Omniverse’s structure.
Multiverse is sometimes used when referring to the Omniverse. You know when the Omniverse is being referred to, whenever it mentions Alternate Realities and Timelines as a whole. Also, Dimension and Universe get exchanged throughout the series, some Timelines get called Dimensions as well.
Known Alternate Universes are Rex’s Universe, the Null Void, Ledgerdomain, The unnamed Universe with weird physics, Dimension 12, Dagon’s World and the 99 unnamed Dimensions Dagon conquered (Dimension and Universe get exchanged throughout the Franchise, also some Timelines get called Dimensions as well)
Known Alternate Timelines to Ben Prime’s Timeline are the No Watch Timeline, Gweniverse, Dimension 23, Mad Ben’s Dimension, Eon’s Timeline, Race Against Time Timeline, Bad Ben’s Timeline, Nega Ben’s Timeline, Benzarro’s Timeline, Time Heals Timeline, Paradox’s Failure Timeline, Argitrix Timeline, the defeating Vilgax without destroying the Omnitrix Timeline, Negative Alien X Timeline, Reboot Tomeline, Maximilian’s Timeline, Ben X’s Timeline, Ben 10,000’s Timeline, Ultimate Ben’s Timeline, Ben 10k’s Timeline, and the however many Timelines Eon enslaved.
Alien X no sold the Anihilaarg (a device that can either create or destroy an entire universe) and literally recreates it from scratch just by thinking about it.
stopped Galactic Gladiator’s Attack with one hand
Created hundreds of copies and then defeated Galactic Gladiator
Not only that a mere fraction of his arm was able to pierce through a higher dimensional barrier where the Contemelia (5th Dimensional Beings) stated that it was “impossible” to breach through making Alien X infinite 5D.
Powers, Abilities, and Hax
Special Abilities: Superhuman Physical Characteristics, Invulnerability, Flight, Reality Warping, Creation (Alien X has the ability to manipulate reality to the way it sees fit. Recreated the entire universe with only its thoughts), Size Manipulation (Grew to the size comparable to a galaxy when fighting The Galactic Gladiator), Existence Erasure (It is implied that Celestialsapiens are capable of erasing things from existence), Multiple Personalities (Has alternate personalities, such as Serena, the 'voice of love and compassion', Bellicus, the 'voice of rage and aggression' and Ben Tennyson himself, who's the 'voice of reason'), Mind Manipulation (Mentally controlled the Amalgam Kids to make them fight amongst themselves), Space-Time Manipulation (Serena states that Alien X could easily change the very fundamentals of Space and Time if they desired to), Pocket Reality Manipulation (It is shown that Alien X's interior is a pocket universe that is big enough to contained compressed galaxies and stars), Acausality (Singularity; According to WOG, there are no past, present or even future iterations of Alien X. Those who transform into Alien X, whether it be in the prime universe or any alternate universe, become THE Alien X and not A Alien X), Telekinesis (Threw around the Amalgam Kids with his telekinetic powers), Duplication (Shown to have replicated itself in order to fight The Galactic Gladiator), Immortality (Types 1 and 3), Regeneration (High-Low), Physics Manipulation, Law Manipulation (According to official sources, Alien X is capable of changing the nature and rules of mana across the universe), Life Manipulation (Can manipulate mana, which is life itself and is akin to the life force itself). Resistance to Time Manipulation (Naturally born in a void without Time and is shown to be unaffected by Time) & Existence Erasure (Was unaffected by The Annilharg's erasing abilities and other Celestialsapiens are unable to remove each other)
Scale
Destructive Ability: Multiverse level
Speed: Infinite (Celestialsapiens are born in and live in the Forge of Creation, a dimension outside of time and space)
Lifting Ability: infinite
Striking Ability: Multiversal
Durability: Multiverse level
Stamina: Infinite
Range: Multiversal+
Intelligence: Omniscient
In Conclusion: Multiversal+