Tessa

In the present, Tessa wears a tinted oxygen helmet similar to an astronaut's, that covers her entire face with a small rainbow and smiley face sticker on the top right side of the visor. She also wears a JCJenson branded cap and a large, light grey bow on the right side of her helmet. Her outfit consists of a short-sleeved, white crop-top like jacket with a shiny silver leotard underneath. She wears a pair of moderately long white gloves that are yellow at the ends, and silver pants with knee-high strapped boots. Finally, she has a golden name tag, showing her name and occupation, and carries a broadsword on her back attached with silver straps.

Tessa makes first appearance in a flashback at the beginning of Heartbeat, when N has a dream about his past life as a Worker Drone still working on Earth.

In the past, Tessa was fascinated by Worker Drones and would adopt or rebuild them from local landfills, often playing dress up with them and even going out of her way to give them hair (which other humans, such as her father James, found creepy). From the expression that J gives upon noticing her, she is somewhat of a boss to the various maids and butlers around Elliott Manor. She is accompanied by the newly reborn Cyn, hiding behind her for assurance as she smiles at N who feels a horrible presence coming from the new maid drone.

Tessa makes her true appearance in The Promening, where she arrives at Copper 9 through a landing pod, jumping out and immediately decapitating a Worker Drone on sight, claiming that she and J, who has been reconstructed and accompanied her superior to the exoplanet, have "maintenance work" to do.

Despite not physically appearing in Cabin Fever, Uzi sees a vision of Tessa in the past with her true human form being shown for a few seconds but with her back turned in a dark, abandoned room as she faced a corner, her face is still a mystery. However, upon looking back, the apparition is gone and instead Uzi notices the hand of Tessa's apparition appear behind the corner, shocking her until she realizes that she is alone.

During the events of Home, Tessa is shown through N's memories of his life on Earth due to Uzi's hacking. There, she is shown to see J as her partner while being enamored by N due to him being a "cute butler" but is wary of Cyn since she knows something is wrong with her, secretly working with J to have her locked in the basement because of this. However, she, J and Cyn were locked in their room during the gala by her mother, Louisa, while N faced the worst of it by being chained to a tree in the swamp for the crows to devour his parts. Angered, Tessa blames Cyn for N being punished in her place, only for Cyn to reveal her eldritch form and reassure her that she won't have to discard her pets nor will Cyn discard her as she warns her to stay away from the gala.

Horrified that Cyn will slaughter everyone present, Tessa speaks to J about work-related taboos such as "paid time off" and "attending a union negotiation" which enrages J's due to her workaholic attitude and allows her to break her and Tessa's chains. The duo secretly pass through the upper floors of the mansion, avoiding the guests, as they search for a way to murder a "robochild", coming across a knight stand with an authentic medieval sword and a revolver on a stand, which they momentarily swap, until N finds them and warns them about V being under Cyn's control. They help N to get the key to the basement as Tessa and J rush to the ballroom where they encounter Cyn and she reveals her true form under the control of the AbsoluteSolver, as Cyn tells Tessa that she didn't have to see this, before she proceeds to murder everyone and leaves her as the sole survivor of the massacre.

Back in the present, Tessa and J meet with Doll who obtained the Keybug from Uzi as part of their deal for taking her with them to the Cabin Fever Labs, despite Tessa shooting her to make sure she wasn't like Cyn, to Doll's annoyance and anger. Regardless, the trio proceeds to head out until they're stopped by N, V and Uzi who confront them for answers.

Although Tessa is first seen as a rather intimidating and mature during the ending of The Promening, Tessa seems to be a very lively and prideful individual. This is demonstrated in Episode 5 where Tessa screams "N" in excitement and spins him around very energetically. This is further shown in Episode 6 where Tessa shouts "N! You remember me. (cough) Tall, handsome, air's toxic" with the same energy she had when she was in Home. Tessa also seems to be somewhat overconfident and proud of herself as she stated in Dead End, "Human made security! This human can control!" with pride and confidence despite not actually gaining control over the Sentinels. Tessa also has a bit of an immature and rather childish personality that heavily resembles her past personality as a child

The scene picks back up at the beginning of Dead End, where N realizes that Tessa is still alive and she, joyfully, tries to pick him up only to momentarily choke on "toxic air", before she is bit by Uzi in anger at a human being on the planet and questions why she and J are here. Unfortunately, before anyone can say anything, Doll betrays the group by snatching the Keybug and running to the lab before them as J tries to stop her while the others make chase with her but are unable to stop the Russian drone from making her way underground.

Daisy Rose, her voice actor, has confirmed that Tessa is an Australian/Aussie. This presumably makes Elliott Manor located somewhere in Australia. She enjoys fixing broken drones and giving them names and human hair, something other humans disapprove of. Despite originally appearing as an antagonist due to her supposedly violent and abusive nature towards the Worker Drones along with the rest of JCJenson, she is later revealed to instead be very fond of these robots despite how much it upsets her parents due to them being disgusted of her habits of "humanizing" them. Due to opposing Cyn and the AbsoluteSolver, she is instead seen as an overarching protagonist of the series. This is later proven in Dead End that her motives for killing a Worker Drone was due to suspicion for the AbsoluteSolver's influence. The gun Tessa acquires in Home is a black powder Colt 1851 Navy Revolver, although in the show it is treated as a cartridge converted version.