Takemikazuchi Shrine

Takemikazuchi Shrine was a temple area temporarily located in Fake Nazarick in Mass for the Dead.

Background
When Nazarick was invaded by a strange Chaos Beasts, some sort of phenomena proceeded to alter not just the minds of the NPCs, but also the internal layout of Fake Nazarick into a place of New Year festivity and atmosphere. According to Momonga the phenomena seems similar to a high tier spell of [Creation] or [Change The World].

Mass for the Dead Arc
Coming across the shrine where Cocytus and Narberal Gamma are station, Momonga and his allies are barred from going any further unless they battle. The group defeats the two and are allowed to pass where they meet with Yuri Alpha and Lupusregina Beta. When Yuri is asked why she left her post, Yuri replies that it was a holiday. All in all Yuri and Lupusregina appear to be mildly affected by the New Year atmosphere. Though they invite him to write his aspiration for th new year though they are suddenly attacked by Chaos Beasts. After dispatching the monsters the group continue to participate in the festivities before heading through the Gate to the 10th Floor. After the Ruler of New Year was defeated, Fake Nazarick had been restored to as it was.

In another reality, Shiramochi-ō descended into a similar world to the previous world in which he was defeated previously. After assuming a new body, the Ruler of New Year lost his memories. Yet despite his inability to remember who he was, the event scenario for the New Year event proceeded. Cocytus and the Pleiades like the previous reality fell under the influence of the "New Year's mood" which compelled them to enter the Hatsumōde to act as it guardians. Shiramochi-ō who took the identity as Shiro and joined forces with Momonga to rediscover who he was encountered Cocytus guarding the temple area. When the 5th Floor Guardian stated that he was guarding the "Takemikazuchi Shrine", Shiro corrected Cocytus stating that the previous incarnation was a flawed work, due to the influence of the local god Warrior Takemikazuchi. The shrine in which he acted as gatekeeper in this reality was in fact the true temple, and the Bishamonten Shrine.

When New Year’s returned, Shiro along with his friends from Nazarick entered the Chaos Realm to confront his double Shiramochi-ō. To initiate the start of the boss fight, Shiro used his partially restored power to cause the Takemikazuchi Shrine to manifest in the space, causing Cocytus to be delighted at the structure at it reminded him of his creator.

Layout
The temple was created on the 9th Floor of Fake Nazarick, when the entire layout of of Fake Nazarick was changed by the Ruler of New Year. The dungeon was converted into a realm with a hazy sky, misty fog, and desolate sands. The Takemikazuchi Shrine was the only structure that existed in the desert dimension. The Gate that was normally used to transport to other Floors was located in the shrine and led directly to the copy of the Throne Room where Shiramochi-ō waited. The roof of the shrine possessed an ornament that was similar to Warrior Takemikazuchi's horns.

Trivia

 * The location seemed to be based on Kashima Shrine, where the shrine is dedicated to Takemikazuchi-no-Ōkami, patron Japanese deity of martial arts. In addition, the shrine is said to be a pilgrimage location for thousands during the New Year celebration.
 * According to the protagonist the area may be a special Chaos Zone created by a Crack as it creates strange humanoid shadows like the latter when it casts light.