Do it for the Beast

From the designer:

Then the strange man, still holding my wrist, drew his knife across the palm of my hand. Before the pain could set in, the most wondrous thing happened! A red serpent, bright as blood slithered from the wound, and rose in my hand. I was transfixed, but the strange man seemed unsurprised. "You can stay with us," he said, "or you can leave and return home. But whichever you do, you must do it for the beast."