- "This goes all the way through to the other side. So, I figure, there's a bloke somewhere around New Zealand standing on a bridge like this one, looking back down at us. All the way down. There's a hole in the world. Feels like we ought to have known."
The Deeper Well was the burial ground for the Old Ones, where thousands of sarcophagi containing the corpses or essences of these ancient and powerful demons were kept to prevent their resurrection. Illyria, who had been assassinated by her enemies, was one of the Old Ones interred within the Deeper Well.
The Deeper Well could be accessed by two entrances: a cave beneath a tree in the Cotswolds and in the Cotswolds antipode in New Zealand. It ran all the way through the Earth, close to 8,000 miles.
The Well was protected from trespassers by a chosen warrior of good and a small army. Drogyn the Battlebrand was the Well's keeper in 2004 and had been so for some decades. It was also guarded by demon guardians. Drogyn later fled his post in fear for his life and was killed by his friend Angel who was scheming to be accepted into the Circle of the Black Thorn.
Knox, the Qwa'ha Xahn (high priest) to Illyria conspired to remove her sarcophagus from the Well and deliver it to Los Angeles, where Illyria was successfully incarnated once again in human form. Angel and Spike, two vampires who were friends with Fred Burkle, the woman whose body Illyria stole, ventured to the Well in hopes of learning of a means of saving her but turned around when they learned it would be impossible.
Buffy, Willow, and Xander later travelled to the Well in the hopes of finding enough mystical energy within to allow Willow to heal Dawn. In parallel, Simone Doffler and Severin also ventured in; Severin hoped to find magic enough to travel back in time and avert the Twilight crisis. Simone entered with an ulterior motive: to release the Old One Maloker and have him transform her into a vampire, as he did the very first vampire. Illyria's council also followed Buffy inside when they learned of Severin's plan. On their way down, Willow sensed a powerful magical source which she believed would not only heal Dawn but also restore Earth's magic. Eventually, a new Seed of Wonder, one that would save the world, but not fully mature for a thousand years, was spawned from Willow's body, draining her powers in the process; Willow proceeded to plant the Seed in the Well. Using all the magic he absorbed from the Well and the many other mystical beings and demons he encountered, Severin managed to age the new Seed to completion. The resulting burst of magic killed both Severin and Illyria and collapsed the Well's entrance.
- "A Hole in the World"
- "Shells" (Only mentioned)
- "Power Play" (Only mentioned)
- "Illyria: Haunted, Part Two" (noncanon)
- "Illyria: Haunted, Part Three" (noncanon)
- "The Core"