Medusa is shown to have a small army of familiars at her command confined in her body. In contrast to her usual nature, she is shown to be motherly to them, more so even than to her real child Crona. Since she breeds them inside her own body, they probably view her as their mother. She keeps her favorites as tattoos on her arms. They can change to suit her needs and perform many different tasks such as spies or assassins.
After Medusa implanted her snakes into Eruka, the fellow Witch is forced to serve her despite her apparent loathing for her. Medusa seems to enjoy picking on her and likes to stand on her in frog form, claiming it feels good on her feet. As a result of Medusa's infiltration of Shibusen and generally risky research and plans, Eruka thinks of Medusa as highly dangerous and threatening to the Witches.
Though, she also seems to hold a great respect for her, even saying so after she believed Medusa was killed by Spirit and Stein. In the anime, after Medusa is converted into her younger form, she actually combs Medusa's hair for her in a big-sister fashion.
When stopped by Mizune and Eruka during the Witch's meeting about her theft against Maba, her bringing a non witch, being a spy at the DWMA as a nurse, and her attempt to create a kishin. When Eruka was in the middle of saying that Medusa should go somewhere else so she wouldn't endanger their kind, Medusa simultaneously shoves both her hands in Eruka's and Mizune's mouths.
She belittles both of them by telling them that they are only their witch's motifs, a frog and a mouse. She reveals she would enjoy inflicting punishment upon both of them, however, she tells them she is currently busy as it was time for her shift at the school. When confronted again within a alley, Medusa pretends to play innocent and ask why they are about to kill her. Eruka tells her she wants to kill her so the witches won't be endangered with Medusa under her alias. Before Mizune and Eruka inflict their fatal attacks, Medusa tells them they need real punishment, as they wouldn't be good test subjects.
When Eruka realizes that Medusa's snake tattoos disappeared, Mizune screames in agony, imploding from Medusa's snakes she swallowed after the witch meeting. Her death was kept hidden from the other Mizune sisters. The Mizune sisters made a alliance with Medusa during Shibusen's Anniversary, in which the sisters used their magic to spread chaos and terror in Death City while Medusa and company went to revive the Kishin. Medusa would use the Mizune sisters on multiple missions such as the Runaway Express to retrieve the Eternal Spring, infiltrate Arachnophobia, and protect Crona during his/her fight with Black Star and Tsubaki; implicating that Medusa has faith in the Mizune's sisters in completing important tasks.
Medusa sent Eruka to free, Free from his prison cell in order for him to help complete her goal in releasing the Kishin with his trademark weapon, Maba's eye. On first meeting when Free expressed his gratitude and wiliness to help, Medusa replied with a sincere smile that all she wanted was a easy task of killing a certain technician and weapon for her. Her hidden intention by doing this was to record the results of Soul's newly implemented black blood. During Shibusen's Anniversary, Medusa's plan to release the Kishin takes affect when Free uses Maaba's eye to create the Independent Cube to trap the staff and students within the DWMA ball room while they traveled under the castle to where Asura was imprisoned.
Once realizing a few members of the DWMA had escaped, she sent Crona, Eruka, and Free ahead of her while she planned to kill Stein, Maka, Death the Kid, and Black Star. In both the manga and anime, after taking over Rachel's body, Medusa orders Eruka and Free to infiltrate Arachnophobia. In the manga, this role was expanded when a temporary alliance was formed between DWMA and Medusa. Medusa trusted in Free to destroy tower 1, but would later get lost and appear at tower 2. This resulted in Free helping Death the Kid destroy tower 2 while battling Mosquito.
Befitting the Purple-Dyed Clown's placement as a creation of Medusa, it obediently follows any order given to it by her, no matter what this might actually entail. With this in mind, Medusa observes the creature as nothing more than a simple tool that will become expendable the moment that it has fulfilled its usefulness.
Medusa appears to be interested in Stein, even inviting him to join her during their battle for the revival of the Kishin. Her sister, Arachne, calls her out on her 'crush', to which she claims that it is Stein's creativity that is appealing to her. She's been bothering Stein in attempts to drive him mad. Stein does everything in his power to keep Medusa from breaking him.
Medusa uses Soul as a Black Blood experiment. It is worth noting that she treated Soul with care when she was using him as an experiment.
As a school nurse, Spirit adored Medusa as yet another random woman he enjoyed surrounding himself by. However, upon finding out that she was actually a Witch, his attitude towards her changes as she reveals her true personality. The defining moment of how Spirit came to hate Medusa is that of when Stein questions her on what exactly she plans to do with her child, Crona, once she is finished with the experiment that she had needed him/her for. Upon responding to this question with evil laughter, Spirit immediately becomes angry, and commands her to stop. After she explains that she will abandon Crona, Spirit leaves his Death Scythe form to walk up to Medusa, grab her, and personally express his disgust towards her. He states that as a parent, he cannot believe that a person would be so evil and heartless as to abandon her own child, and that the action is unforgivable. After defeating Medusa, it is implied that Spirit shows no form of regret for defeating someone he had formerly been lightly attracted to, as Medusa is the only person that Spirit has actually shown to hate.
Medusa can easily predict Spirit's behavior, and not only his lustfulness but his engagement with the DWMA's typical humor annoys her. When he fixated on the bloomers she wore while possessing Rachel Boyd, Spirit managed to agitate her so much that she pointed her Vector Arrows at him, even when standing in front of Death himself.
Like many enemies of her, she dislikes him immensely, though not in the manner Arachne does. However, he's the only character in which she has been shown to act more civilized and respectful to (without it being a ploy). This is due to her great fear in dealing with him, knowing how much he would have her killed with his power. She has also openly expressed fearing him, and even fears his infamous Shinigami Chop. In all, she views him as a major force in keeping the world from evolving.
Maka begins the series looking up to Medusa as a school nurse. However, after Medusa's evil intentions and plans came into play, Maka quickly became the person who hated her most. Maka's hate for Medusa continued growing stronger the more she had seen Medusa tormenting Crona. In the anime, Maka even makes it her number one goal to defeat Medusa at any cost even if it means she has to disobey orders.
Arachne is the older sister of Medusa. The sisters are more than happy to manipulate each other as pawns in their plans and do not seem to hold any concern or regard for each other. On the contrary, the Gorgon sisters would seem to be rather hateful of each other. Whether this began before or after Medusa's betrayal of Arachne to Shinigami is unclear.
She is third of Gorgon Sisters, alongside Medusa and Arachne. Due to her youthful appearance, she is presumed to be the youngest of the siblings. It is unknown how Medusa treats her, as they were never seen together in the series.
Medusa is the mother of Crona but this title holds little relevant value to how their relationship functions, as she sees her child more as research material than an actual person. She sometimes shows concern when he/she is in danger, however this might just be because, for her, Crona is valuable research subject. She used to force him/her to carry out cruel killings of helpless animals in different ways. When she was fighting Stein she claimed that if Crona fails to become the next Kishin, she was going to get rid of him/her. whether this means just abandoning him/her or outright killing him/her is not made clear.
In final stage of her experiment involving Crona and Black Blood in the manga, she breaks his/her mind by showing him/her motherly affection. Unable to accept this new feeling from her, Crona falls into pure madness and murders her. Despite this, Medusa is proud of him/her and silently declares her love for him/her for finally achieving his/her purpose, which is completing Black Blood and becoming the tool of "evolution" for the world. She also proclaimed she loved Crona.
In the anime, Medusa ultimately has no problem trying to kill Crona when he/she rebels against her to save Stein. And when she seemingly mortally wounds Crona, this entices Maka's fury against her. However when she did "kill" her child, she even admitted that she never thought Crona would die saving another person's life.
While not much was mentioned about her she was the girl who was possessed by Medusa when she lost her body to the battle with Stein. According to the anime/manga this little girl was shopping with her parents and found a dog during a walk amongst stores so she walked up and began petting the dog when Medusa's snake entered the little girl's body. All that is known is that during the little girls battle against Medusa's control is that she watched TV right after. As she watched the TV screen: she kept repeating a scene "I want an apple" as a young woman pick an apple with a snake next to it in her head (most likely). Her personality is curious and easy to manipulate as Medusa later points out "She is a good little girl; very easy to manipulate." -Medusa. It points to her basically being Medusa's tool like the purple-dyed-clown.