The Lake of the Lost Sea is in the centre of the great marsh of Deathmoor.[1]
This is the tiny remnant of the lost inland sea of the Stargazers. It is said that on the edge of the lake a hero found a small skiff, of ancient design but beautifully preserved, which provided passage to an ancient long ship of the Stargazers which had been used for a royal burial.
The whole of the marsh of Deathmoor is the remnant of an inland sea around the edges of which was built the towns and cities of the Stargazers in ancient times. In the Time of Heroes some great Evil befell the civilisation. Although we do not know the details, it seems that some great sorcery-filled battle ensued, destroying much of the towns and cities of the Stargazers.
Great beasts known as Flesh-Eaters appeared on the coasts of the inland sea, patrolling it and preventing the civilisation regaining a foothold. Those people that escaped became nomadic. The inland sea was polluted and defiled and reduced in size, the majority of it becoming but a marsh. Those lands that had once surrounded the sea became riven with mists and magical energy, and are now known as Deathmoor. Only the very centre of the sea remained as the lake.