The Well in Ethbir

The Well, built in Ethbir ,

A 13 sided temple, being opened on a religious ceremony amplified by a shooting star...
Has 13 sides, houses 13 ancient famous paladins, 1 of the graves is empty, known as the knights of Ethbir, founded the city after they expelled the ancient evils that resided here. 
May house the book of vile darkness, with the keys hidden in each of the 6 main temples in the city