The Chernobog!
It is nonsensical to think that it does not possess a Lethal Venom Sac.
Surely somewhere in its body there must be naturally produced poisons alongside the concentrated poisons derived from consuming the Deadly Mandrake.
My research over the past eight years confirms this.
However, I don't know the exact location because I haven't dissected one yet.
I, Aku Foiron, will find a Lethal Venom Sac in the Chernobog!