Characters

Ben Tennyson
Ben fills the role of leader after Max disappears. The Omnitrix has been recalibrated, giving him access to a new set of alien heroes. Over the past few years, Ben has matured dramatically.

Gwen Tennyson
Now 15, Gwen is much more proficient with her powers, able to manipulate energy directly as opposed to using spells (this is revealed to be due to Gwen having an alien heritage),where she can manipulate energy to create blasts, shields, and energy like grapple holds. Although she's not nearly as fiery or short-tempered as before, Gwen is still always looking out for her cousin. She also is presumed to have feelings for Kevin Levin (below).

Kevin Ethan Levin
A former nemesis of Ben, Kevin is now getting by as an alien tech dealer. He unintentionally gets involved in the Highbreed plot, and joins Ben out of a desire to make up for his actions. His abilities now allow him to absorb the properties of any solid matter he touches. He has feelings for Gwen, but is somewhat shy about it and over the course of time, the pair have started dating.

Max Tennyson
Max is a semi-retired member of the Plumbers. He disappears while investigating the Highbreed plot, leaving only a few cryptic messages for Ben to find. He is briefly reunited with his grandchildren in "Max Out", but sacrifices himself to destroy a Highbreed factory at the end of the episode. In the episode "Voided", Ben and Max reunite in the Null Void, and he promises Ben that he'll come back soon. He eventually returns in the second season finale of the show, "War of the Worlds" to aid Ben in his final assault against the Highbreed

Julie Yamamoto
Julie is Ben's current love interest and later becomes his girlfriend. She enjoys tennis, eating chili fries, and caring for her pet, Ship (an alien Mechomorph found by her and Ben).

Highbreed
The Highbreed believe themselves to be the purest of all species, and intend to cleanse the galaxy of impure lower life forms. Earth is their current target. It's later revealed that they are dying out, having lost their resistance to disease due to heavy inbreeding, and that they intend to destroy the rest of the universe with them.

DNAliens
Hybrids of humans and alien drones that serve the Highbreed, the DNAliens are able to disguise themselves as humans using special identity masks.[1]

The Forever Knights
A secret organization that has worked in secret ever since their formation in the Middle Ages. The Forever Knights will trade alien technology with anyone who's willing, even the Highbreed.[1]