The Antitrix is a makeshift replica of the Omnitrix's season 1 model, with the dial symbol turned red and appearing in half, resembling a letter 'K', and with the addition of four metal protrusions ending in red lights.
The Antitrix is a DNA-altering device, using the cross-contaminated mutated alien DNA it contains to transform the user into a monstrous mutant of any of the 11 hybrid aliens in the device.[DR 1]
Unlike the Omnitrix it is modeled after, the Antitrix only possesses 11 aliens, instead of many aliens organized into sets of 10.[DR 2]
The Antitrix has a quick change feature, allowing Kevin to change forms by pressing the symbol on the aliens' chests.
There is a secondary method for using the quick change feature by mentally choosing the next alien.
The Antitrix symbol is generally located on the chest of the transformations.
Between the events of Seasons 2 and 3, the Antitrix was created by Kevin when he gained the blueprints of the device in a dream. However, the boy arrogantly decided to make minor modifications to the device, making the aliens Kevin becomes somewhat different and more powerful, than their normal variants, but also unstable.
The Antitrix can keep Kevin transformed for much longer than the Omnitrix. This is proven in certain episodes, as the screen-time for an Antitrix alien is equivalent to the screen-time of two Omnitrix aliens.
The Antitrix has been referred to as such only in marketing. In the series, Ben and Kevin both refer to it as an Omnitrix.
The Antitrix is similar to the Ultimatrix in several ways:
Both were created by a villain, who took the basic Omnitrix blueprint/core and added extra features onto it by themselves.
Both of them make the aliens more powerful in combat.
The creators of both are, in some ways, a counterpart of Ben.
The Antitrix is also similar to the Biomnitrix in the sense that the transformations are fusions of any two species.
Kevin and all his aliens are voiced by Greg Cipes.
Kevin modifies the Antitrix on a regular basis.
Theoretically, the Omni-Kix feature could work with the Antitrix, but the latter is not the exact copy nor does it have the same internal workings as the Omnitrix, so the Omni-Kix feature would likely not work with the Antitrix.[DR 3]