Ceroba

Appearance Ceroba is a fox-like monster with beige fur and long, wavy ginger hair. Her hair is tied up in a ponytail by a red ribbon with a small gold bell in the centre. She has a long, white kimono with red trimmings; a red obi sash tied around her waist and white boots.

During her battle phases, she carries a long red staff with a bright yellow bell at the end two little red ribbons tied around the ends of the bell. In the Pacifist Route battle, she wears the Kitsune mask made by Kanako, consisting of two dark eye sockets that receive bright red dots in the final phase, with pink dyes. Her hair becomes more voluminous, resembling tails with pink shine. Additionally, she wears a cloak that is shown in concept art to be yellowish-white with pink edges.

Her attacks in the overworld are represented as white and pink flashes of light. Brilliant, supportive and skeptical, Ceroba is a powerful ally when it comes to wanting to help those closest to her. She is shown to care a lot for her loved ones. However, she is highly stubborn, even going so far as to question the true meaning of Asgore's words when confronted with the truth of her husband's employment. Because of this, she is firm on her husband's legacy as a scientist and a hero of the underground, and she spends the days after her husband's passing trying to complete the work that he had passed down to her. However, when she finally tests it on Kanako and has it result in her falling down, Ceroba's beliefs strengthen to the point that she is fully willing to kill Clover to save the rest of the underground.

Ceroba is observant, and can tell how others are feeling just by a glance, and can also notice a shift or change in the other's moods. Though she is not hesitant to say them to others, she will try to hide them from those she loves as long as it does not harm others. An example of this is her relationship with Starlo, and she didn't confront him about his behavior until after his friends had come up about how it was making the rest of them feel. She is quite honest and straight-forward as well. This is evident from how she treats Starlo's shenanigans in the Wild East, saying she doesn't understand it and acting nonchalant when included in them, as well as her realistic assessment of Clover's fate before and after her battle in the Pacifist route. The exception to her realism is her husband, Chujin, who she always holds in high regard no matter what information is displayed to her that may say otherwise.

Ceroba Ketsukane (穴金 セロバ) is a primary antagonist (along with Flowey) in Undertale Yellow.

She is the widow of Chujin and the mother of Kanako. Her main Intent is taking Clover's SOUL to save the underground and advance Chujin's legacy, and she serves as the final boss of the True Pacifist route, and penultimate boss of the Flawed Pacifist route.

During the Genocide route, she replaces Starlo as the boss of the Wild East after Clover kills the latter in a duel. Clover first meets Ceroba in the Wild East. Ceroba formally introduces herself to Clover after Clover is taken to the saloon. She requests that Clover entertain Starlo, and in return, will see what she can do with letting them leave. Ceroba appears during most events with Starlo and the Feisty Four, and Clover is usually able to talk to her afterwards. After the battle with Starlo, she requests for you to accompany her through the Steamworks and to the lab in order to find Kanako, whom she hints to Starlo and Clover is still alive. Ceroba sends Starlo back to the Wild East and is with Clover for the majority of the Steamworks. While traversing the Steamworks, she reveals bits of her past. When the pair reaches the elevator on the other side of the Steamworks, they're confronted by Starlo and Ed. Here, it's revealed that while trying to arrange a party, Ed discovered something hidden within her house. Ceroba appears to panic and runs into the elevator, leaving Clover with Starlo and Ed.

When Martlet and Clover find Starlo confronting her, she tells Starlo and Martlet to leave Clover with her. When negotiations break down, she strikes down the two of them before they can interfere. She then tells Clover they are naïve for thinking five humans could be alive in the Underground, or that Asgore would let them go. Admitting to be a hypocrite and not morally superior to Asgore, she states that she will help Monsterkind by using Chujin's work, stating that if Asgore did break the barrier, humans would just defeat them again and stuff them back down into the mountain. She admits to having nothing else to lose before attacking Clover.

Halfway through the fight, Clover unlocks the ability to shoot larger projectiles, forcing Ceroba to use Kanako's mask to achieve a Kitsune-like form. Clover eventually cracks the mask, which causes a memory to play out before the two of them. The memory is of Chujin on his deathbed, who tells Ceroba of the bunker where he worked on his project, with Kanako having heard everything. Ceroba is initially startled by Clover being in her head, but continues fighting. Clover manages to chip away more of the mask, revealing another memory of Ceroba and Kanako in Chujin's bunker, with the young girl naively allowing Ceroba to inject her with Chujin's serum, causing her to "fall down". As Ceroba lays silently before Clover, she reveals how deep her sins are and is "chasing the one ray of sunshine peeking through the surface", unable to let go, and gets up one last time.

Eventually, Clover manages to destroy the mask, reverting her back to her normal state. As Ceroba lays defeated before Clover, she eventually realizes her attempts at fulfilling Chujin's legacy were at the cost of her family, and made her attack her friends and a child, for something that may not have even worked. Wracked with guilt, she begs Clover to finish her.

If killed, she thanks Clover for freeing her of this guilt, happy to be reunited with Chujin again. Upon her death, she drops Kanako's broken mask.

If spared, she begs Clover to finish her, before being interrupted by Starlo. After Martlet wakes up, she apologizes to Clover for attacking them before Clover hugs her as an act of forgiveness. However, she shoots down Martlet's suggestion of presenting Clover to the King, and eventually gets in an argument with her and Starlo for Clover's future. When Clover decides to sacrifice themselves so that one day, Monsterkind can be free, Ceroba is the only one who accepts Clover's intent. After sharing one last hug with the human, she extracts their SOUL before saying farewell.

During the credits, she's comforted by Starlo just before presenting Clover's SOUL to Asgore. Later, she is seen getting corn from the Wild East and delivering it to Dalv's new home in Snowdin. Afterwards, she shows up with Dalv in tow so that they can say their farewells to the human.