The Seven Headed Hydra

When the sorceress, Sapphire Circe, first read of the Hydra in one of the esoteric books she had recovered from the lair of the Minotaur, she of course assumed it was merely a poet's metaphor for any problem that gets worse when you apply force to it. At best, she thought it could have been a repeatedly amplified rumor based on maybe a drunken encounter with a large crocodile, perhaps.
But the book's author seemed to know what she was talking about when it came to other magical creatures of myth which Circe had already learned were all too real.
Many armies and businesses had used the symbol of the Hydra in various ways over the years, with its number of heads varying as needed for artistic purposes, but in all fanciful incarnations, the idea that it could not be killed (not easily at least), or even became more powerful the more opposition it met.
However, there was the small detail that Hercules (everybody's hero) figured out how to defeat (kill) the beast. Fire applied to it's eight severed necks prevented two new heads from growing from the stumps. And (with a magic sword given to him especially for this purpose) he cut off the last head (called "the immortal head") and buried it under the road between Lerna and Elaeus. The body, with all the head stumps cauterized, died, and Hercules used the beast's poisonous bile to power up his arrows into poisonous insta-kill arrows.
Immortal head. That was it. What if the body was not going to regrow the last head? What if that one special head was going to grow a new body?
The legend named the location the head was buried. If no one in all these centuries had unburied that head, then she could retrieve it.