Eunice

Eunice, otherwise known as the Unimatrix, is a living prototype Omnitrix created by Azmuth. She can absorb and contain DNA of various different species and use their abilities. She is a close ally of Ben's team and currently works as Azmuth's assistant.

History
While still in her Unitrix form, her pod crashed into Earth and was discovered by Ben, Gwen and Kevin. When Gwen touched the pod, it cut her hand and The pod then opened (while releasing a green gas) to show a beautiful, and completely naked blonde girl, that of which became Eunice.

Eunice later gained consciousness, and Ben gave her his jacket to cover herself so she wouldn't be seen naked (though it only helped with covering her upper body). They went to the forest and asked her who she was, but she couldn't remember anything only that her name is Eunice (it's actually Unitrix, but she can't remember it right). She and Ben started to bond very quick and started liking each other (remember, Ben recently broke up with Julie until later on in Season 2). She went back to the car with Gwen to give her some proper clothes (a simple pink tank top, white pants and sandals). It was shown that alot of animals were literally attracted to her. Even ones that were normally shy around humans. When they go fishing, Ben and Eunice started to get along very well, and their crushes on each other grew. One night, Ben and Eunice were walking to a ravine. When Ben went uphill to see where it was, a bear appeared from the bushes and looked as if it was going to attack Eunice. Ben, noticing this, transformed into Armodrillo to save her. He drilled down the hill and jumped out of the ground, ready to fight the bear. However, much to his shock, the bear didn't harm her. Instead it was attracted like the other animals, and it was letting her pet it. Ben changed back and asked her how she did that. She claims that she didn't do anything, but just knew it wasn't going to hurt her. Ben then went to show her where the ravine was. While he wasn't looking, a green flash shined from Eunice's hand while she was still touching the bear. She then followed Ben and absent mindly pushed a boulder out of the way.

While Ben and Eunice were walking to the ravine, Eunice stopped to look at blue flowers. Then, a group of rabbits gathered towards. Ben still couldn't figure out how the animals were attracted, yet she didn't know either. She picked the rabbit up and asked Ben if he wanted to pet it. He asked if it bites, and she said no. But she was sure that the bear he was gonna fight for her does though. Ben claimed that it was different, but Eunice told him that if he wanted to be scared of the rabbit she wouldn't judge. He began petting, as she asked, but then put his hand on her hand. She noticed this, looked at him passionately, and the two started to kiss each other on the lips as they were intimate proximity. However, it was interrupted when Sunder gave out a warning shot. Ben turned into Spidermonkey, went ultimate, and fought him. Ben at first thought that he was after the Ultimatrix, but Sunder revealed that he was after Eunice. He then knocked down Ben to the ground, and started take Eunice. But before he did so, Eunice touched the rabbit she was holding, and like the bear a green flash shined from her hand. She then put it down, and started jumping very high, and escaped Sunder. He looked at her jumping, and was shocked after seeing that. Ben then jumped him, and started fighting him again. Unfortunately, he changed back and Sunder started chasing after.

Ben then went back to camp, where Gwen and Kevin were, for some help. Luckily, Gwen was able to sense and track her since Eunice was wearing her extra clothes she gave her. They finally tracked her to a mountain high up. It was then that Sunder found them again, grabbed Eunice and pressed a rectangular button behind her neck, which changed her into an Omnitrix core. Ben turned into Cannonbolt, went ultimate and fought Sunder. Gwen and Kevin arrived and helped defeat Sunder, and change back Eunice.

Azmuth arrived at the scene and revealed that he hired Sunder to retrieve Eunice. He also reveals that Eunice is really the "Unitrix" - a prototype model of the Omnitrix. Instead of a device that would store all DNA in one place, Azmuth originally planned to store the DNA in individual containers, in other words, the Unitrix's. It is also revealed that Eunice's human form was actually from Gwen. Apparently, when Gwen cut her hand on the pod when she first touched, it was really sampling her DNA, randomized it (modify into a completely different sample, a lot like the Omnitrix when it acquired a new sample) and created Eunice. He came to take Eunice back to Galvan Prime to put her back in storage, which frightened her. Ben, who had grown close to and cared about Eunice, refused to let Azmuth do so. Azmuth, under Ben's compromise, allowed Eunice to be one of his assistants as he always needed of a helping hand on taking care Primus, and then leave.

Characteristics
Eunice has very similar functions to her successor, the Omnitrix (making her slightly akin to a living machine), only that she is an individual container, and can only store one sentient DNA sample, which acts as her mobile or general form. In this case, her general form is an adolescent human, as Gwen was the first sentient life form to touch her pod, which sampled her DNA, and birthed Eunice.

Eunice is somewhat like Gwen's biological daughter (being created entirely from her DNA), but she is not truly Gwendolyn's clone, as her DNA was scrambled extensively to make it very different, and thus had to alter an rearrange Gwen's genes to give Eunice phenotypes that her template lacked; specifically recessive traits like Eunice having blonde hair, and notably contrasting chin shapes (Gwen's chin is rather squarish while Eunice's is more sharper, pointier and more attractive). The two things they do share are similar face structures, but most of all their unique green eyes, which Ben and Gwen's brother Kenneth share.