The Bakunawa died at the beginning of the Age of Gods and fell into the ocean. The Bakunawa died on the Night of the Shattered Moon devouring the moon goddess Thaya. The Bakunawa is a beautiful woman who lived in the ocean. The Bakunawa is a serpent large enough to eat a moon. The Bakunawa is a weapon of war created by the Aberrations of the Far Realm. All of these things are true at the same time.
I saw the Bakunawa's Grave once when I was a little orc in Borthakar. It opened up in Reaver's Deep on a new moon. Me grampy orc tore his muscles rowing out boat away from a boiling ocean full of angry coiling undead snakes. That's the first time old Sgt. Kill Flayer ever felt fear.
The Bakunawa's Grave appears in large bodies of water throughout the world whenever the new moon is dark in the sky. The Bakunawa materializes in the water in various stages of dying, death, decay, or unlife. It's death was so momentous, it echoes throughout time forever. Sometimes the headless coils of a gigantic snake lay motionless under miles of water. Sometimes a gasping fanged head breaks the water spurting black acidic blood. Others report seeing unending dead coils thrashing the water, creating tsunamis.
The rarest version of the grave is when the battle between Thaya and the Bakunawa is recreated in the heavens. The constellations come to life and depict the goddess trapped in scaly coils cutting her way out with her curved blade.
Reports of the grave appearing come from all over the world. From the tropical reefs of the Talinian Ocean to the cold white icebergs of Reaver's Deep. Large inland seas and freshwater lakes have all manifested the Grave at some point.
Scholars, priests, and poets all have their own theories about how and why the Grave appears. Wizard's claim that the temporal echoes between the Bakunawa's two known deaths mixed with the unborn god-moons it devoured send it throughout the world's timeline. Priests claim that the Bakunawa is cursed by the divine energy it consumed and that those gods still want to be born into the world. The poets say that the song of the Seven Moons demands to be heard.
The Grave is extemely dangerous and it's appearance is treated as an omen of ill luck. Monsters commonly in the days after the Grave shows up. Dead fish poisoned by the venom of the dead snake litter the water and nearby shores. No one who has entered the Grave has ever returned. Many explorers and great heroes have been lost trying to unlock the mysteries of the Grave.
The great serpent that ate six of the seven moons before being slain by Thaya, the last moon goddess.
Ginunting ng Thaya
Slain moon goddess. Victorious serpent. Fallen sword, glittering to the surface of the moon. It waits for a worthy hand.
The elves patrol the dust of the broken moon seeking vengeance for the death of the Silver Lady.