Sanctuary

The Sanctuary (聖域) is a secret magic facility for the Cult of Diablos's experiment. Aurora state that the Sanctuary is a memory prison, created from ancient battles.

Overview
The Sanctuary is a place not at all physical, but magical in its isolated magical sub-space within the land of Lindwurm that cannot be physically entered. Except through the magical door that will open in response to the Goddess's Trial or within the Lindwurm church gate, but that gate is only available for the Cult of Diablos members which they can have access to enter the Sanctuary.

History
The Sanctuary is place where the hero Olivier is said to have cut off the left arm of the demon Diabolos and sealed it at Lindwurm. Although it is considered a sacred place in the Holy Church, it is actually like a graveyard because many magic swordsmen were defeated during the Diabolos War and their memories and residual magic remain.

Once a year, there is a battle event called the Goddess's Trial. When a fighter's strength exceeds a certain level, a warrior spirit matching that level appears and fights against that warrior spirit.

In reality, it is a place where the cult researching Demon Possession and sealed the Diabolos remains during the Diabolos War about 1000 years ago, also a graveyard of ancient memories and demons' burning grudges. It was concealed in the form of a seal by using the land where residual magic power was staying. There were devices such as holy swords that could only be used by specific humans and chains that could only be cut by those swords.

The Cult are able to successfully seal the demon remains away by using a high-grade powerful artifact. However, the sealing was imperfect, and its generated distortions will eventually became the Sanctuary.

Functions

 * Memory Recall: Can be able to see the memories in the Sanctuary. However, it is not possible to confirm every memory to know how far it is true, because memories can change over time as they fade with time, reshaping themselves to fit their owner’s narrative.
 * Ghost Prison: It is speculated that in certain cases, the Shrine can permanently retain sentient souls fragments of the individual who is imprisoned within the Shrine, up to their entire soul. When Cid Kageno entered the sanctuary he was met by the conscious fragment of Aurora, who according to her was locked inside the sanctuary for 1000 years.
 * Defense System: The defense system will reject every abnormalities in the facility by using a memory that reacted to them and materialized to prevent from entering further to the center. Nelson explains that the closer they are to the center of the Sanctuary, the more of their power is drained. Alpha adds that at the same time the closer is Nelson to the center, he gains more power, which is understood, since the sanctuary territory of the Cult means that its members can use the powers of the sanctuary to their benefit the further inside they are within it.
 * Ghost Memorial Copy: As the sanctuary is a prison and a cemetery of ancient memories, it can be created and invoked a memory puppet of the warriors who perished in past battles that the sanctuary kept as memory, and hundreds of copies of this, this is seen when Nelson invokes a soulless Olivier memory fragment, as such, which only serves to kill anyone that Nelson or the cult members order him to, to undo members of the Shadow Garden.

Weakness

 * Although the Sanctuary was created by the Cult as such, even if it is its territory, by using the power of Aurora as the nucleus for its operation, Aurora, over the centuries, managed to manipulate certain rules of it and be able to bring and search for someone with enough power to free her, being in the end Cid Kagenou.
 * If the Sanctuary center is destroyed, then everything inside will be released, including the diablos remain which have been sealed.

Trivia

 * In the Light Novel and Manga version, it is depicted as a medieval alchemy workshop. But in the anime version, it is depicted as a facility with advanced science and technology that is now lost.