Sergei Kravinoff was a skilled hunter in Africa, descended from Russian nobility. When hunting became prohibited Sergei became a guide. He met Mariah Crawford when she travelled to Africa to investigate after Dr. James Reeves went missing while researching in the jungle. Mariah and her team hired Sergei to guide them. Sergei acted as her bodyguard against the wild animals of the jungle, and he and Mariah fell in love.
Months later, they found Reeves, who had developed a formula to protect himself from infection in the jungle. However,
a side effect meant that he had turned into a feral creature. Before disappearing forever, Reeves gave Mariah the last of the drug, warning her not to use it on herself or another person under any circumstances.
Sergei was seriously injured trying to protect Mariah from a pack of hyenas. It seemed that there was no hope for Sergei to survive, but in a desperate attempt to save his life Mariah gave him the wonder drug. He made a full recovery, but gained feral hunting instincts as Mariah had feared, and became Kraven the Hunter
Mariah travelled back to America to work on a cure for Sergei, who also returned after thinking that she was seeing another man. He confronted Mariah, demanding the truth. Spider-Man interrupted and fought Kraven, with Kraven eventually disappearing and Spider-Man having Mariah hide in his friend Robbie's home. However, Mariah was eager to get back to her work on a cure quickly and left, returning to her lab. Her scent led Kraven to Robbie's, and Kraven believed he was Mariah's "other man", kidnapping Robbie, and telling Spider-Man that he must bring Mariah to him to ensure his
his friend's safety. Spider-Man did so, and after Kraven was defeated Mariah gave him a serum to cure him, and the two returned to Africa. Mariah later went to Africa to help people who were suffering for an unknown virus. However, she contracted the disease herself. Sergei gave Mariah the serum which she had once given to him, which had saved his life but also turned him into Kraven. It was at this point that the same procedure that Sergei had endured happened to Mariah, who turned into a feral creature even more deadly than Kraven was, Calypso. Calypso fled, and Sergei was forced to become Kraven once again to stop her. The creature then began to attack people. Once the creature was killed, his wrath was focused on Spiderman, who had interfered.