Roswaal L Mathers/Relationships

Echidna
Somewhere in the past, while Echidna was alive, she took Roswaal as her apprentice. After her death, Roswaal became obsessed with reviving her and killing Volcanica.

Beatrice
Being an acquaintance of his master Echidna, Beatrice and Roswaal simply maintain respect towards each other, however, Beatrice didn't tolerate to see how he never cared for her except for Echidna. That fact changed over time after the events at the Sanctuary.

Hector
Somewhere in the past, Hector was pursuing Echidna and Roswaal tried to beat him in a fight, but he ended up badly wounded. Since then, Hector became his rival. Also, Roswaal started to wear clothes and talk like him.

Volcanica
Volcanica is the one that kept Echidna's soul in her grave, which was also the reason Roswaal wanted to kill Volcanica.