The ruin that birthed a society; the Life and Times of a city in the throes of death.
Triastu. The City of the Three. The Hallowed City. Triastu is the holy city of Trianarianism, and is the home of the Trirex. Many have paid homage to it, and many have gone on pilgrimages to it, and have marveled in its beauty.
Sid and Jir were childhood friends growing up in the same town on the ocean. Both creative geniuses, both with the need to be better than the other. Many will tell you that this friendship created their genius while others realized, in hindsight, that it spelled the lands doom.
If you want to add a "supernatural" touch to your campaign, define the rules of magic and the universe. Make your players comfortable with those rules. Then your new supernatural creatures must then break those rules.