The remnants that lay within Rell can tell you that even still, the inhabitants are deeply connected to their gods, which explains why the artifacts located there are so powerful. Stories of a mask that will show anyone who looks at the wearer their greatest fear, a flute which was said to have been used by the gods to create the wind, and so fourth.
It is hypothesised that these powerful relics came with a price, debilitating curses. Permanently losing vision, sacrificing a family member, forever smelling like a corpse. These relics likely attributed to the strength of the old kingdom, but the curses led to the empire’s downfall as well