To the world, the gods' blood is toxic. That's the general belief most people hold in the world.
Because nothing was free and for the strength this blood gave to mercenaries that wish to fight off the threat against humanity, it was all worth it.
The head that Immortal stole and the samples in the hand of Mehendati commerce that were obtained through various means which also included the apostle of sands who once acted as Alfin's girlfriend. All of them had poisoned samples.
Alfin was an individual that lived side by side to poison since the day he injected himself with the original gods serum.
But this poison was not always in his blood. Wilkis and his daughter Farsight had already secured pieces of untainted Alfin's blood and flesh before they poisoned him with Death Wood.
And they were working on their own methods to weaponize it. And the path came to fruition after they obtained the research notes on cloning from Reina that also brought a lot of other things with her.