Prince Vivescu is an exiled prince of Romania/Serbia (of a noble line of the Banat or near it), also called Prince Moni. He is a charismatic libertine, accompanied by the thugs Cornablue and La Salud.
- In a Montparnasse tavern he tries to poison the group with suspicious phosphorescent liquor. It fails; Claude resists.
- Philippe seduces him to investigate. In his luxury hotel suite, raving under substances and poison, he says the Serpent offered him fortune, inheritances and a ready testament for information about the vice-consul in Bucharest, and that perhaps he should finish him.
- Philippe finds letters confirming a train trip to Bucharest and correspondence with Bandi/Bandica (accomplice or lover), and persuades him to take Philippe along as valet.
- Vivescu travels on the Orient Express, governed by the Serpent’s will, a puppet of a larger conspiracy. He is linked to the “Circle of Serbia”; a connection to vampirism and dark forces in Bucharest is possible.