At some point during Hanzō's childhood, he found a black salamander with deadly venom residing in his village.

Some caecilians, the alpine salamander (Salamandra atra) and some of the African live-bearing toads (Nectophrynoides spp.) are viviparous.

Genetic studies have shown that the closest relative of the island’s salamander would be the black salamander from the Alps, branching off five million years ago.

As a child, Hanzō was implanted with the venom sac from a black salamander, which resided within his village upon its death, leaving an identifiable scar on the left-side of his abdomen.