Tomb of Ariel (Nightmare)

The great black pyramid called the Tomb of Ariel was not the place where the Demon of Dread was buried. Instead, it was a place he built to bury unbearable truths. The one who was buried at the heart of Ariel's Tomb was Oblivion.^[1]

When the ever-present mist was gone, the brightness of the day appeared. Amidst the clear, sparkling water, seven suns illuminate the sky and the flowing water. One sun, rising from the waters to the right, paints the sky and water with soft lilac colors, turning the world into a vibrant blue. Far left, another sun drowns in the bloodred water, turning the world into a fiery crimson light. The eastern horizon is at dawn, and the western horizon is at dusk.^[2]

The inner wall of Ariel's Tomb was covered by a massive swarm of Dark Butterflies, these Great Monsters were seemingly asleep on the black surface.^[3]

Main article: Estuary

Main article: Great River

In an unknown region of Dream Realm where countless Nightmare Seeds seemed to be blooming. It was a vast desert covered by eerie ruins with a giant black pyramid that sometimes appeared as a haunting mirage^[4]

The path to the tomb is only visible from certain parts of the desert.^[5]

“	Time within the Tomb of Ariel is unpredictable and convoluted. Sometimes, it flows slowly, while sometimes it flows swiftly. Sometimes, time rises in great storms, or grows stale, or circles forever as a whirlpool. Currents merge and separate, or disappear without a trace. But, nevertheless… for most of us, unless we enter turbulent waters, time always moves. Just like in the outside world. It is just that our own time is different from the time there.	”
― Ananke about the time within the Tomb of Ariel, Chapter 1292 History of Time

The time within the Tomb of Ariel is unpredictable and convoluted due to all sorts of flow and current of the Great River but it has past, present, and future in relation to itself, just like in the outside world. The Great River does flow from the future into the past, but that is only in relation to the outside world. This kind of time is no different from space.^[6]

In short, there were two concepts of "time" inside the Tomb of Ariel — one was the flow of the Great River itself, which was prone to all kinds of shenanigans, while the second was no different from the concept of time humans are familiar with.^[6]

Main article: River People

The River People lived differently due to time working differently for them, and the first settlers of the Tomb were all Outsiders.^[7]

In the Tomb of Ariel, both the human settlements and hazardous environments were constantly shifting as cities migrated and dangerous areas changed or moved.^[8]

According to the rune description of Graceless Dusk, the Tomb of Ariel seems to have existed for a very long time prior to then. It wasn't said how the daemon died or if the pyramid can possibly be his tomb, and who would build him an opulent grave.^[9]

The Tomb of Ariel was built from the Stone Titan's remains, while the Great River created from its blood was contained within it, illuminated by seven suns from its broken soul cores. Ariel wished to forget the truth and hid that secret at the Estuary, while the Nightmare Desert was the result of his battle with the unholy creature.^[10][11]

• Two more dreadful places within the Tomb of Ariel: the far reaches of the future upstream and the far reaches of the past downstream.^[12]
• The tomb revealed that simply knowing certain things could corrupt living beings.^[13]
• The idea of solar year was meaningless inside the tomb because the Riverborn children grow up physically by travelling upstream, which for the River People akin to seasonal changes.^[14]