So I don't always create my own monsters. Sometimes I re-cycle from other sources, something I'm not alone in. As I researched creatures for my books, I recognized several from Harry Potter. Because sometimes, the sources for monster and creature ideas can be found in ancient Greek Mythology. Stories rich in character, monsters, places. Timeless stories about the human nature told in the fantastical or grotesque depending on the plot.
I borrowed the idea of Tartarus Prison from Greek mythology. Hades's underworld, a place where once you enter, you can never leave and Hades's rules with an iron hand. No one ever escaped. In my Urban Fantasy, the prison houses the worst of the worst in demons, vampires, dark wizards. So horrendous, no one would ever want to find themselves there, a place that could turn a rather normal person crazy nuts. It is magic you know.
Who should guard such a place filled with the mystical creatures? It can't be the mere mortal, the one who lacks the strength and agility to handle the multitude of beings that pass through the doors. The logical choice could have been Cerebus the three-headed guard dog which defended the entrance to Tartarus. Though it would be borrowing from Greek Mythology and fit in my story, it would be taking from Harry Potter, too new to not be considered stealing.
I ran across the story of the Hundred Handers. The three children of Gaia the Earth Goddess and Uranus the Sky God. Their children so ugly, fierce and frightening, their father tossed them into a pit in Tartarus. They sought revenge against their father, eventually fighting with the Olympians and against the Titans, for control of the universe.
I've asserted in The Day of First Sun, that the giant guards were descendants of the Hundred Handers, with less arms and heads, mere giants, big and strong enough to handle the creatures that paraded through the prison on a fairly regular basis.
Greek Mythology allowed the ancient Greeks to explore and explain the world. I wondered, what would vicious fifty headed, hundred handed creatures be trying to explain. Their mother loved them regardless of their hideousness, their father threw them into a pit. Experts suggest that because these were considered the first beings created from procreation, and their parents disagreed on their care, it caused fighting between the Gaia and Uranus. In other words this is the first instance illustrating marital strife.
There was always a reason for the stories, an explanation, a lesson to be learned if you know where to find them.