The Atlantians & Their Lost City

Tales ago, stories spoke an underwater kingdom, which sunk when a great serpent, wronged by the king of Atlantis by stealing the bones of its children from the den of riches it provided, to make a trident to command the waves, wrapped around the landmass and dragged it underwater. With the power of the trident, the king sacrificed himself and killed the serpent wrapped around the city by diving into its belly and killing it from the inside. A final curse from the serpent was that none would ever return home, and thus merfolk were born. The poisonous blood enshrouded the city, having the people leave and never return as the corpse bled endlessly.
As the story goes, at least.
Tales passed and the city was left in the depths of mythology. However, the quest for Atlantis is a story that quested for by even land dwellers. This is not a story of archeology's sake, but for fame and fortune. The city, still filled with the riches of the gifts of the serpent before the betrayal, also holds the trident which commands the waves, tides, and all creatures of the deep. But as dangerous as the story's serpent, new threats fill the deep, perhaps a curse ensuring the legacy is forever lost and forgotten.