[quote=@Psyga315]
So... Shall we speculate about how the Hydra ties into the challenge thematically? I'm guessing it has something to do with the many heads and having too much of it.
[/quote]

That seems the most logical explanation. The more skilled you are in slaying beasts, the more dangerous the hydra becomes.

But if we [i]really[/i] want to push it—Hercules dipped his arrows in the venom of the slain hydra, which he used repeatedly in his following labours. Their deadly properties were quite helpful. His last kill, however, was Nessus, a centaur. This centaur convinced Hercules's wife to fashion his skin into a coat to give to Hercules, and when he put on the coat, the venom that had killed Nessus then killed him.

But really, I think it's actually what you suggested.