There is purposeful vagueness and double-meanings in the OP to reflect a sort of metaphorical understanding. It's purposefully written not to be clear because the fictional book(s) the passages are from were compiled long-after the fact. So they come with no immediate understanding of who or what the Visha were.

Sort of like how the Huns were described as apparently only having the ability to "cry blood" or something. When in reality they probably just cut their cheeks to force bleeding to replace tears when in mourning.