Eunice

Eunice, also known as the Unitrix (short for Unimatrix) is a prototype Omnitrix which can absorb, contain and recall the DNA of different species.

Backstory
Eunice is the Unitrix created by Azmuth, which is a prototype of the Omnitrix. Sunder was hired by Azmuth to find her when Azmuth lost her. Her pod was discovered in the forest at the same time Ben's Team was driving for a camping trip. After encountering her, she stayed with them for the day, bonding with Ben (who had recently broken up with Julie), the two of them were soon attacked by Sunder, who shut Eunice down and attempted to get away before Kevin and Gwen stopped him as Ben restarted the Unitrix again.

While the four of them scuffled with Sunder in a field at the base of the mountain, Azmuth arrived and cleared things up. He stated that Eunice was actually a Unitrix, a prototype version of the Omnitrix created when Azmuth wanted to preserve alien DNA by placing genetic samples of sentient and non-sentient life forms in individual containers that can animate themselves to take on the appearance, and use the abilities, of the DNA samples that were uploaded into them for protection. Azmuth states that when Gwen cut her hand trying to open the pod containing the Unitrix, her human DNA was sampled and randomized to make a human form for the Unitrix to use for mobility (explaining why Eunice has blonde hair while Gwen has orange/red hair). Following a brief argument, Ben allowed Azmuth, under a compromise, to take on Eunice as one of his assistants on Primus.

Appearance
Eunice's mobile form is a teenage human girl. She has shoulder-length blond hair with a single bang and bright green eyes. When they first found her, she was completely naked, then she borrowed Ben's jacket so she wouldn't be naked. Afterwards she borrowed a pale pink tank top, white shorts and brown flip-flops from Gwen. Since working for Azmuth on Primus, she adopted a white jumpsuit with black stripes.

In her true form, Eunice is the Unitrix, a core similar to the Omnitrix and Ultimatrix. However, the core resembles a container instead of a watch, but does feature a control dial that, when pressed down, turns it to its mobile DNA form (in this case, Eunice).

Powers and Abilities
As a prototype Omnitrix, the Unitrix is capable of storing DNA of different species. Unlike the Omnitrix and Ultimatrix, she is not connected to the Codon Stream or Primus, limiting it to a single DNA sample. Eunice was also shown to be able to absorb DNA and powers of several animals (a rabbit, a bear, and a snake) and then to manifest traits of these animals (great jumping, increased strength and abnormal flexibility, etc.) without changing form. The powers and abilities she absorbs from aliens and animals last for about ten minutes. There is also a green rectangle on the back of her neck and when Sunder pressed it, it turned her back to the Unitrix.

In addition, local wildlife seemed to be attracted to her to the point where normally shy animals would gather around her and render more dangerous animals (like a bear or snake) docile towards her and others (this capability was likely included by Azmuth as a way for the Unitrix to easily obtain DNA samples from them, possibly to protect her and the item from danger since it's only temporary and the Unitrix can only contain one DNA sample).

She also received an upgrade to have a one way subspace link to Primus for uploading DNA samples. However, having the link active can cause parallel signal interference which could cause the Ultimatrix to lose its connection to Primus until it's shut off. She also has high knowledge of the Ultimatrix.

Appearances

 * The Transmogrification of Eunice (First appearance)
 * Simian Says

Trivia

 * Eunice is the only character shown naked during the series.
 * According to Dwayne, whatever Eunice absorbs, she only has the abilities of it for ten or so minutes, like the Omnitrix and Ultimatrix.
 * According to Azmuth, Eunice is dangerous. According to Dwayne, we will see why, probably meaning Eunice will return.
 * Interestingly enough, Eunice's jumpsuit looks like a combination of Ben's soccer shirt and Danny Phantom's jumpsuit before he gained his ghost powers and the colors were inverted.
 * An interesting fact is that Eunice is almost nothing like Gwen, she has blond hair (opposed to Gwen's orange/red hair). This is because her DNA is randomized. She has not got Gwen's Anodite powers, because the Unitrix only absorbed DNA from Gwen, and since Anodites don't have DNA, Gwen's DNA is 100% Human. However, Eunice and Gwen both have green eyes, a common trait in the Tennyson family.
 * As Eunice's mobile form is made of human DNA, it would technically make her Azmuth's first known human assistant.
 * Eunice is technically related to Ben and Gwen since she has Gwen's DNA. This was said by Azmuth explaining that the Unitrix sampled then randomized Gwen's DNA into her own unique human DNA and created Eunice.
 * As the human DNA being sampled and stored, Eunice has in a way technically fulfilled Azmuth's original function for the Unitrix. So you can say Eunice is now a preserver for the human race. Despite the device being a prototype model of the Omnitrix even though the Codon Stream already has human DNA being preserved in it. She did however receive an upgrade to have a one way subspace link to Primus for uploading DNA samples, allowing the Unitrix to be used beyond its original intention.
 * Eunice's mark on the back of her neck resembles the brand of a Pulse l'cie from Final Fantasy XIII.
 * The reason why the Unitrix landed on Earth is because it was seeking an Omnitrix core like itself and the Ultimatrix has an Omnitrix core.
 * At the beginning, Eunice's origin was kind of similar to Supergirl's arrival on Earth; she appeared in a space pod, she was fully naked, she had the DNA of Earth's heroes, and she didn't know what was happening.
 * Eunices' role in the series somewhat mirrors that of the character Nia from the series Tengen Toppa Gurren Lagann: both were/are artificial life-forms imbedded in the human genome and both have a relationship with the protagonist (Eunices' relationship to Ben being a minor one)
 * If Ben or Kevin had touched the space pod, Eunice would have been male. If Kevin touched the space pod, it is unknown if Eunice would be a full Human, full Osmosian or a hybrid like him.
 * Eunice being afraid to go back into storage is similar to Jessie from Toy Story 2 being afraid of being put into storage. They are both artificially made.
 * If Eunice's DNA sample gets altered or corrupted, it can be repaired by turning the Unitrix off and back on again. With some help from its later model the Ultimatrix
 * In both of Eunice's appearances, Ben becomes Ultimate Spidermonkey.
 * Azmuth originally planned on building a separate device to store the sample of each species.