Osmosian

Introduction
Osmosians are a species of parasitic aliens that dwell on the distant planet Osmos (Aggregor once referred to it as Osmos V). The names "Osmosian" and "Osmos" are a play on the word "osmosis", the name of the physical process by which a solvent (i.e. water) diffuses from an area of a high concentration through a semi-permeable membrane into an area of low concentration. It is also the process by which living cells absorb water and nutrients.

Powers/Abilities
Osmosians have the unique ability to absorb any type of existing Mattermatter or energy through their bodies at will in order to utilize it in various ways. This includes electricity (and possibly any energy within the electromagnetic spectrum), the DNA, life force, metabolic energy, and powers of other life forms, fire, water, plasma, and the mass and physical properties of solid matter. Since everything contains either matter or energy, there is no limit to what they can absorb.

As demonstrated by Kevin in Ben 10, when Osmosians absorb energy, they can use it to activate and overload machinery, discharge it as energy blasts, or use it to temporarily boost their strength and haling capabilities. They can even store energy for periods of time. However, the energy will dissipate over time or through excessive use, so they are required to recharge from a reliable power source.

If an Osmosian were to absorb raw energy (such as the energy of the Omnitrix or Ultimatrix) and can not control it, the energy will cause the Osmosian to become mentally unstable. Storing that same energy for periods of time will only worsen their instability unless they quickly discharge it or their body uses up all of the energy. Because of this, they can eat food like other species and feed off of life force and metabolic energy of other life forms as their primary sources of sustenance to keep their hunger for raw energy latent. When an Osmosian has recently absorbed raw energy, they will have black rings around their eyes. (Kevin had these rings around his eyes during the original series as did Aggregor in Ultimate Alien.)

While overindulgence in energy and storing it for periods of time can cause Osmosians to become mentally unstable, it is possible that an experienced and mature Osmosian, like Devin or Aggregor, knows their limits and can control their cravings and discharge energy better than a young or inexperienced one, who give in to their cravings whenever the opportunity presents itself and do not when to stop. This explains Aggregor's behavior and is why he was so desperate to obtain the newborn Celestialsapien's incomprehensible and immeasurable powers and abilities. This also explains why Kevin began absorbing the life force of whoever he came across to satisfy his insatiable hunger in Absolute Power Part 1 and Absolute Power Part 2 and how his sanity was immediately restored after he was drained of the energy he had absorbed.

As demonstrated by Kevin in Alien Force, Osmosians and half-Osmosians are able to absorb the mass and properties of solid matter and grow an armor-like outer skin as durable as the material used to make it and by extension proportionately enhance their strength and durability to even higher levels. Osmosians can extend their armor to anything they are touching when absorbing matter, as demonstrated by Kevin in Plumbers' Helpers. While absorbing matter, the Osmosian can also momentarily merge with the actual matter and alter its form by releasing a liquid version of whatever substance they have absorbed and hardening it again. After absorbing matter, the Osmosian can temporarily absorb extra mass to gain limited regenerative abilities as well as shape-shift its limbs into various weapons, tools, and forms.

As seen in "Kevin 11" and Escape From Aggregor," when Osmosians absorb the DNA, life force, and metabolic energy of other life forms, they gain most, if not all of that life form's powers (or at least their primary abilities). However, they can only acquire the original creature's powers at 1/10 of their original potency without mechanical aid (this is the biological limit for Osmosians) and can only use them temporarily unless they were to absorb all of that life form's DNA, life force, and metabolic energy, leaving behind nothing but a shrunken husk. Regardless of how much an Osmosian absorbs, their own DNA will eventually overwrite the alien DNA in time, causing them to lose their absorbed powers and return to their normal form. The amount of these energies an Osmosian can absorb at once, as well as the extremeness of their mutation, depends on their age and experience. (When Kevin absorbed the powers of Heatblast and Four Arms, he appeared to be an incomplete version of those aliens and only retained his powers for less than thirty minutes. However, when Aggregor absorbed the powers of a Geochelone Aerio, his appearance stayed the same though he could now grow six hollow ports on his torso to create wind attacks or fly at will and retained his absorbed powers for well over 24 hours.)

If an Osmosian were to attempt to absorb the life force and DNA of several life forms at once or the energy of the Omnitrix or Ultimatrix, they will become a chimerical fusion of most, if not all of those creatures. While they are powerful in these chimerical forms, their powers are still only 1/10 of their original strength. However, because they are a mixture of aliens, they can mix and match their abilities to make up for their reduced potency (such as Kevin using Heatblast's flames and Stinkfly's goo to form an explosive attack or combining Four Arms' strength. XLR8's speed, and Diamondhead's invulnerability for, as he put it, "one mean punch"). In addition, their mutant form limits their ability to utilize the special powers of the aliens they have absorbed; being a random fusion of aliens, they cannot utilize the powers that are not prevalent to their mutant form unless that power does not require a specific organ or appendage (Ultimate Kevin was able to use Echo Echo's sonic scream despite not having any of his characteristics on his mutant form).

As seen in Ken 10, whenever an Osmosian takes on a chimerical mutation caused by absorbing the DNA and life force of several life forms at once, they can willingly shift between their normal form and mutant form once their DNA has fully restored itself. (Dwayne McDuffie confirmed that during the flashback in ...Nor Iron Bars a Cage, Kevin had managed to change back to his human form once (which explains why he was wearing jeans instead of cargo shorts) before becoming stuck in his mutant form again due to his age and lack of experience and control.) They will retain that mutant form so long as they use it periodically. Even after the mutation has worn off, the initial transformation leaves its genetic imprint on their DNA, even after their own genetic structure has overridden the alien DNA. This means that the mutation can be passed down to their offspring. This is shown with Devlin, who has the unique ability to shift between his father's first mutated form and his human form at will.

Even without absorbing energy or matter, Osmosians possess a minor degree of super strength and durability. While not on the same level as Tetramands or Petrosapiens, they are still stronger and more resilient to damage than an ordinary human. This has been repeatedly demonstrated by Kevin, who, even without absorbing matter or energy, is strong enough to lift and throw the combined weight of several people and resist physical trauma that would severely injure an ordinary human with moderate discomfort. According to Dwayne McDuffie, an Osmosians strength and durability does not solely come from the energy and matter they absorb; rather they possesses a minor degree of super strength and durability in their normal form that is simply increased whenever they absorb energy or matter.

Little else is known about Osmosians so far, except that they are outwardly indistinguishable from humans except for the fact that Osmosians live for hundreds of years, and after about one hundred years when an Osmosian is fully mature, they begin to grow small horns.

Weaknesses
Osmosians have few natural weaknesses. While they are still stronger and more resilient to damage than an ordinary human in their normal form, they are largely powerless without matter to absorb and must have a decent amount of said matter to completely encase themselves and utilize their matter-based abilities to their full potential,

An Osmosian's biggest weakness is their insatiable hunger for raw energy (though it is normally latent and becomes easier to control if they are mature and have had sufficient experience with absorbing energy). The more energy they absorb (with the exception of the DNA, life force, and metabolic energy of other life forms), the more they lose control, thus hindering their ability to think properly and eventually causing them to revert into a primal state of mind. Their insatiable hunger for raw energy (and the subsequent mental instability) stays latent if they avoid absorbing raw energy at all cost.

Any powers an Osmosian has absorbed from other life forms will begin to wear off and eventually disappear as their DNA restores itself in time (unless they use the absorbed powers periodically). The more life force, metabolic energy, and DNA they absorb, the longer it takes for their absorbed powers to wear off.

Trivia

 * It is confirmed by Dwayne that absorbing energy makes all Osmosians insane, mature or not. He also confirmed that Osmosians normally don't absorb energy unless they are put in a situation were they absolutely have to.
 * Kevin Levin, one of the main characters, is a human/Osmosian hybrid; his father (Devin Levin), was an Osmosian, and his mother (Mrs. Levin) is a human.
 * The potential danger from a premature Osmosian's physical and mental state from absorbing raw energy would explain Kevin's lacked control of transforming into Ben's original ten aliens and then mutation whereas his older, more experienced future counterpart could freely control his absorbed powers. It also explains his aggressive sociopathic behavior in the original series but later becoming relatively well-moraled after returning to his normal physical self. Aggregor however is unaffected by this as he is both already amoral and power-hungry to begin with, as shown in Ultimate Aggregor. It is possible that the degree of insanity affects each individual Osmosian differently and that a mature, experience, and strong-minded Osmosian is more level-headed and less aggressive than a younger one and are able to retain their sanity for short periods of time.
 * It can be determined from Ragnarok ("Your an Osmosian."), P'andor ("I did not realize there was an Osmosian on this planet"), and Aggregor's ("You're a long way from home") surprise to learn that Kevin (an Osmosian) was on earth, as well as Kevin's response to Galapagus's claim that he was kidnapped from Aldabra by Aggregor ("An Osmosian? Doubt it.") that Osmosians rarely leave Osmos.
 * In Ultimate Aggregor, Aggregor disagrees with Kevin's belief that uncontrollably or improperly absorbing raw energy causes insanity in an Osmosian. He states that this is simply a lie told by the strong to control the weak. It is likely his own personal belief and Kevin is more right than he realized as Aggregor's personality is very similar to Kevin's when he went though his first and third mutations (though Aggregor is not nearly as violent and aggressive and much calmer and level-headed than Kevin was, possibly due to his experience and advanced age).
 * As seen in Escape From Aggregor and Absolute Power, Osmosians are parasitic by nature, feeding off of the life force of other life forms as their primary source of sustenance, killing their victim in the process(during Absolute Power, Kevin seemed to be absorbing life force to satisfy himself rather than for simply the sake of becoming more powerful). However, when they absorb raw energy (such as the energy of the Omnitrix or Ultimatrix) without restraint, this method of feeding turns into an addiction, causing the Osmosian to become insatiable and seek out the largest source of energy they can find. This explains why Aggregor was so desperate to absorb the newborn Celestialsapien's unlimited energy and incomprehensible and unimaginable power. This also explains why Kevin stole the powers of his victims as he killed them (by draining them of life force) and why he became obsessed with draining Gwen of her vast amount of mana as well as her potentially unlimited Anodite and magical abilities.
 * It is confirmed by Dwayne McDuffie that there is Osmosian DNA in the Ultimatrix.
 * In Fused, Aggregor calls Kevin a hatchling, as Kevin's age, power, and experience is far below that of Aggregor.
 * If an Osmosian tries to absorb the power of multiple aliens at once, as Kevin did with the Ultimatrix and Omnitrix, the Osmosian will become a mixture of most or all of the aliens. This happened to Kevin in Kevin 11 when Kevin tried to steal the Omnitrix from Ben. This also happened to Aggregor when he absorbed the powers of the Andromeda aliens in Ultimate Aggregor.
 * The Osmosian home planet is Osmos.
 * Osmosians are more advanced than humans.
 * In "Ultimate Aggregor", is confirmed that Aggregor lives on Osmos V.
 * Dwayne McDuffie has stated the concept of Osmosian's growing small horns as they age is something they thought of after the episode Paradox, in which Kevin was temporarily turned into an old man, which is why there were none on Kevin's head at the time.
 * Dwayne McDuffie confirmed that Osmosians are a little stronger than humans, and are a lot more resilient to injury.

Notable Osmosians

 * Devin Levin
 * Kevin Levin (half-Osmosian)
 * Devlin Levin (quarter-Osmosian)
 * Aggregor