Echidna/Relationships

Roswaal Mathers
Years before the Great Calamity, Echidna encountered a young Roswaal who was unable to utilize his insane magical talent and potential. He was being treated as a sickly nuisance by everyone who encountered him as back then, magic was very much misunderstood and the mages weren't as renowned as they are now (with few exceptions). Echidna sensed his ability and potentially devastating power and decided to take him under her mentorship, teaching him how to properly use magic, opening Roswaal's eyes and allowing him to recognize that his body isn't a "danger" but a "gift", allowing him to prevail and learn how to effectively use all six magical elements. As a result, Roswaal harbored intense and deep feelings for her, which were sadly very one-sided as Echidna is unable to comprehend human emotions. Despite that, she still became the most important person to him, as even after her death, Roswaal became obsessed with reviving her, even being prepared to give his life in order to achieve his desired future and cross paths with Echidna once more.

Puck & Beatrice
Echidna created Beatrice and Puck 400 years ago. Beatrice refers to her as Mother, while Puck does not seem to be so fond of her. Despite that, they both show some degree of respect towards her, Beatrice even considers Echidna to be her actual mother.

Satella
As the Witch of Envy, Satella was involved with Echidna and the other witches' deaths. Unlike the other witches who only despise the Witch of Envy, Echidna hates Satella as well.

Emilia
Echidna claims to have hated Emilia from the moment she first saw her. During her trial where Emilia was forced to face her past, Echidna made several derogatory remarks at the half-elf, mocking her for her dependence on Subaru. Echidna also seems to have some knowledge about Emilia's parents, claiming that she is just as stubborn as her mother. Echidna adds that she personally knows her real mother and that it is one of the reasons for her hatred.

Natsuki Subaru
Echidna is greatly interested in Subaru's Return by Death ability, as it allows her to collect information from multiple points in time. To that end, she invited him to her tea party so in order to strike a conversation with him and later offered Subaru her assistance in the form of a contract. The author has implied that Echidna holds some degree of affection/feelings toward Subaru.

Hector
Hector and Echidna were in some sort of conflict when both were alive. Hector pursued Echidna which caused her to protect herself in the Sanctuary for a time. After seeing Roswaal badly wounded, she decided to fight him, the outcome of the battle remains unknown, though it is certain that Echidna survived, as it is known that she was later sealed by Volcanica.

Pandora
Unlike the rest of the world, Echidna seems at least be acquainted with Pandora, describing her to be the Witch of Vainglory to Emilia during her trial. However, she is dismissive of Pandora's power, claiming that it made her an expert at saving her own skin.

Minerva
Among all the witches, Minerva is on the best terms with Echidna because she likes to take care of people like Echidna. Despite that, she did interfere with Echidna's forming of a pact with Subaru due to her own beliefs and the fact that she wasn't being entirely honest with him.