Baduna Marius was vice-chair of Sorin Carpathia's department at the University of Romania and Sorin's homosexual lover. His relationship with Sorin had gone on several years, possibly longer than Sorin's marriage to Marilena.
Like Sorin, Baduna was married while their relationship went on. Baduna's wife commits suicide after Sorin and Baduna move in together, which he is not affected by in the least as he makes a crude joke about it during a class.
The two men were a part of a project secretly funded by Jonathan Stonagal. He must have been attractive, as it was foretold Nicolae Carpathia's looks would come from Sorin's lover, not his wife.
He and Sorin quit the college and lived off of payments made to them by the organization, until Nicolae decided that his fathers needed to be assassinated.