Ben Tennyson.
Now 15 Ben Tennyson has put back on the omnitrix after complicated removal in the past. Ben now has 10 new aliens. Though his past aliens (Ditto,Grey matter ect.)have been removed from alien selection. He also has a crush named Julie. Now dealing with new enemies such as Mike Mourning Star and the DNAliens Ben Tennyson will stop at nothing to protect earth after the death of his grandfather Max.
Gwen Tennyson
Like Ben Gwen has also has aged into her teen years. She is a master at karate and acrobatics. She is now nicer to Ben and less bossy. In the episode "What are little girls made of?" it's revealed she is part human and part energy being which applies to the fact that she has powers as there is no such thing as magic according to her dad. Her grandma has taken an interest in her since they have the same powers.
Kevin Levin
Now a good guy Kevin joined Ben and Gwen on there quest to protect earth. The RV is gone so Kevin drives around the crew now. He is 16 with a car and a license. He has crush on Gwen though he'll never admit it. He has a plumbers badge that was from Magister a former plumber when he died. He is stronger than he was when he was 11. He can absorb any solid object. Commonly rock and steel. He and Ben fight time to time but as Ben says "He cheats. He lies. That's Kevin."
Aliens.
Swampfire.
Swampfire is an alien that is a combo of Heat Blast and Wild Vine. He can regenerate as he is made out of plant. He can control all forms of plant life and shoot fire balls from his hands. He was Ben's first transformation . His first appearance was when Ben needed to fight the Forever Knights and Kevin in "Ben 10 Returns" pt.1.
Echo Echo
Echo Echo is a living amplifier. His ability is to scream at very high volumes. He also has self duplication abilities. The one that is Ben can be found by a 1 on his back. He can produce a wall of sound allowing him to stop projectiles in midair. His first appearance was when he had to fight a robot controlled by the Forever Knights in "Ben 10 Returns" pt 2
Humongasaur
A strong alien that suits Ben's fighting style. He is dinosaur that has a high level in strength. He can grow huge making him stronger the bigger. Humongasaur is used for the stronger foes and tougher tasks. Ben first turned into Humongasaur when he had to fight Hybrid,commander of DNAliens in "Ben 10 Returns" pt. 2.
Big Chill
Big Chill is an alien with a dark cloak giving resemblance of a phantom. He can fly,invisible and pass through objects encasing them in ice. He also can shoot ice breath freezing them as well.Big Chill's first appearance was to chase Kevin when he stole the RV in "Kevin's Big Score".
Jet Ray
Jet Ray is an alien that can fly at incredible speeds. Unlike Stink Fly Jet Ray glides rather than using wings. He can shoot laser blasts from his eyes and his tail carries a powerful poisen. Another comparasen of Jet Ray and Stink Fly is that Jet Ray is used for self-flight only. His first apearance was when Ben chased Allen in "Everyone Talks About The Weather".
Chromastone
Chromastone is a living crystal that can't be harmed by lasers and light based weapons. Either they reflect as if they were nothing or get absorbed and shot back. His is apparently as strong as Cash (the local bully) with a robot suit.His first appearance was in "All That Glitters" when he was fighting zombified school girls. Chromastone knows himself as a conductor.
Brain Storm
Brain Storm is the first alien Ben thought of a name for. He is a genius and he speaks in a heavy British accent. Brain Storm is cabable of projecting force fields and shooting electricity bolts. He first appearance was an accedental transformation for Jet Ray when he was fighting Ship in "Pier Pressure".
Spider Monkey
Spider Monkey is 4 armed monkey with extreme agility. It can shoot webs jump high. When Spider Monkey talks it's an exited childish voice like the 10 year old Ben. Spider Monkey is the only alien that dosen't revert back to normal in the usual way. His first appearance was when Ben had to fight Grandma Verdona in "What Are Little Girls Made Of?".
Goop
Goop is one of Ben's favorite aliens. Kevin and Gwen though think it's gross. Goop is really a tiny UFO controlling the slime. Goop is also known to shape shift as he can form his body in any way he wants. Goop's first appearance is in "The Gauntlet" when Ben fought a robot.
Alien X
Alien X is an unknown alien and his powers are also unknown. He is only shown in blacken out. Ben has never went this Alien X. He is said to appear in the future episode "Ben Plus X Equals 2".
Enimies.
Hybrid
Hybrid is an alien that is commander of DNAliens, aliens that wear masks making them look humanoid. After Max destroyed the null void it exploded like a hand grenade and killed Max and maybe Hybrid in the explosion. His minions produce babies that are face huggers. They attach to peoples faces and turn them into DNAliens. They can be removed by specail treatment from the omnitrix.