Vasilisa first appeared in Darkness Calls, rescuing hellboy from Koshchei the Deathless via a lamp from Baba Yaga's house. She explains that she gained the lantern when her stepmother sent her to Baba Yaga, hoping the witch would kill Vasilisa. Instead Baba Yaga let her go with the lantern, thanks to the aid of a magic doll. As she finishes her story Koshchei shoots an arrow through her, killing her in Hellboy's arms. With her dying breath she gives him a comb and a handkerchief, that were given to Vasilisa by her doll on her deathbed.
Vasilisa was a handmaiden in Morgan Le Fey's castle.
When Morgan urged Hellboy to seize Excalibur and embrace his legacy as the rightful King of England, Hellboy refused, haunted by his bloody rampage against the giants he had encountered earlier, as well as his unwanted legacy as Azzael's son and wielder of the Right Hand of Doom. But Vasilisa opined that he had been listening too much to Astaroth, Rasputin, and all the others who had insisted on branding him as a monster and an instrument of evil. Vasilisa asked why he couldn't believe what Alice Monaghan, and many others believed: that he was his own man, and able to use his powers for good.
During the final battle between Hellboy's army and the Queen of Blood's, Vasilisa gave Hellboy an iron sword, forged from the raven on top of the Queen's helmet, which Hellboy used to kill the Queen.
Vasilisa's name and appearance are very similar to Varvara, though no clear connection between the two has been established.