Estuary

An enormous black edifice, like a rough, irregularly shaped, giant sphere of black stone that hovered in the void, eternal and indestructible. Its surface was adorned with strange mountains, rising from its hollow interior. It looked like a giant stone heart nestled between massive black stone outcroppings, a vast valley lay beneath the darkness, containing the remains of numerous broken ships.^[3]

In the mountain's hollow peak, a vast circular tunnel was surrounded by tall pillars. The stone steps leading to the tunnel were man-made, possibly daemon-made by Ariel. There were cracks and jagged black stone pieces on the steps, resembling the jagged black rock from which the Key of the Estuary was created.^[4]

The lake hidden in the inner part of the Estuary was connected back to the Great River, creating special connections due to its existence outside of time. Following one of the streams would allow one to exit the Estuary and enter the Great River at a different time, possibly far in the future or past. This allowed the Mad Prince to invade a cycle of the Great River and bring future Plagues.^[5]

There was a wide vertical crack at the base of the slop that looked like an entrance. Inside the mountain was a consecrated place — a place more holy than any temple Sunny had ever visited, and more divine. The sacral nature of the mountain felt strangely mournful.^[6]

A dark cavern vast enough that one could not see its ceiling and its walls drowning in darkness. The floor is covered in shallow water, and a small island rises from the glossy surface at a distance. A beautiful tree grew in the middle of the island, nestled beneath its branches.^[7]

The heart of the Estuary was peaceful, like an island of safety and tranquility in a world full of nothing but dread, yet also poignant and mournful, evoking a sense of melancholy and a sense of sorrow experienced by someone who once resided in this sacred sanctuary.^[8]

There was an unadorned sarcophagus in the heart of the Estuary that remained even thousands of years after the daemons and gods were no more. The sarcophagus was nestled between the roots of an ancient tree. There were no runes or carvings, and no mark left to remember who was buried. Looking above was a golden fruit hanging from a tree branch. The fruit was similar to the one from the sacred tree growing on the deck of the Chain Breaker.^[8]

It is located somewhere in the Great River^[1], the heart of the Black Pyramid.^[10]

The misty place at the beginning of the Nightmare was the outer boundary of the Estuary and the source of the Great River, a place between the past and the future where the laws of time were twisted and broken. The space that existed beyond time was the entrance to the true Estuary, containing Ariel's secrets, which were hidden in the mist.^[11] (Refer to Source of Great River)

The entrance to the Estuary within the Source is difficult to find, but to reach its heart, one must possess three things: a soul free of corruption, the ability to pass a stone maze without falling back into the cycles of the Great River, and the True Name delivered by Torment to Cassie.^[6]

The Estuary existed outside of time or rather, time itself did not exist yet in the Estuary. By choosing the right passage, one could escape the cyclical flow of the Great River and travel to a different time.^[5]

Inscribed on the tunnel walls were dreadful runes that described the Void Beings. Corruption was the influence of the Void seeping through the walls of existence that caged it. Therefore, knowledge of the Void was the source of Corruption as well. Ariel had inscribed the stories of the Void and the True Names of the harrowing beings on the walls of the Estuary. This knowledge, which could be shared and transferred, turned this form of Corruption into an unstoppable infection. The Spell refused to translate these runes, as it would be the end of anyone who did. Moreover, being in the presence of these runes was harmful.^[12] (Refer to Forbidden Runes)

The numerous runes carved into the stone, not only mentioned the Void and the Chaos Beings but also described them in detail and called them by their True Names.^[12]

Main article: Hidden Truth

• Key of the Estuary (Sunny's Memory)
• The black stone found in the hidden chamber of Aletheia's Tower was said to have absorbed the essence of time and had come from the Estuary.^[13]
• The sorcerous ink used to connect the runic circuit of Chain Breaker to the sacred tree was created from the dust of the black stone they got from Aletheia's Tower.^[14][15]
• Daeron's throne^[16]

Ariel had protected the most terrible and precious final secret at the very heart of the Estuary, and only those who pass the guardian's judgment can learn it. That judgment appeared to be a very simple one: an uncorrupted soul.^[17]

• It was mentioned in the rune description of [Stifled Scream].^[1] and [Shroud of Graceless Dusk]^[2].
• It was where Defilement was born.^[19]
• Those who died untimely are sent downstream to return to the Estuary, the origin of everything.^[20]
• The entrance to the Estuary is stationary, but space in the Source is unreliable.^[21]
• The one who was buried at the heart of Ariel's Tomb was Oblivion.^[8]