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 fusion of any two species.[DR 1]
The Antitrix has a quick change feature, allowing Kevin to change forms. This can be accomplished in one of two ways:
The first is by pressing the symbol on the aliens' chests.
Between the events of Seasons 2 and 3, the Antitrix was created by Kevin when he gained the blueprints to 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.
Unlike the Omnitrix it is modeled after, the Antitrix can have 11 transformations unlocked at a time, instead of 10.
The Antitrix can keep Kevin transformed for much longer than the Omnitrix. This 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.