I'm surprised nobody has written a bloody mary fanfic but it's set in medieval times, the eel would be a giant dragon, rocky would still be rocky, and instead of earth being doomed because the sun is dying, maybe it's a dragon called astrophage attacking certain castles.
Maybe Ryland would be a pesant sent off as a knight to slay the dragon (astrophage) or something similar.
Simon would be a prisoner sent off to find the source of the dragon's den (blood ocean or a cave of blood)
Him and grace would meet at the dragon's lair, they'd work together to slay the dragon and decide to abandon their kingdoms and run away to live with the rock people (rocky's people)













