Magnus used it to create a serum that all members of the Five were injected with and which caused unique mutations in each of them: longevity for Dr. Magnus, heightened intelligence for James Watson, the ability to teleport for John Druitt, invisibility for Nigel Griffin, and the activation of dormant vampiric genes in Nikola Tesla, and later when said genes were forcefully removed granted him magnetic powers.
What was left of the source blood was hidden by Gregory Magnus in a secret labyrinth under the ruined vampire city of Bhalasaam. It was recovered by the surviving members of The Five many decades later in order to find a cure for the Cabal's Lazarus virus. However, it was soon stolen and delivered into the hands of the Cabal by Ashley Magnus.
Over a year later, an S.O.S. from Nikola Tesla led the team to a new species of Abnormal centipedes called Multipedes; Tesla had found an old Cabal laboratory where a sample of source blood was kept, which he had hoped to use to reinfuse vampiric powers into his system. When the Cabal destroyed the lab, the explosion infused the local wildlife with the source blood, creating the Multipedes. Henry Foss was eventually able to destroy most of the Multipedes, but Tesla saved one for his experiments, which Magnus intended to confiscate later.