Bishamonten Shrine

Bishamonten Shrine (毘沙門天神社) was a temple area temporarily located in Fake Nazarick in Mass for the Dead.

Background
When Nazarick was invaded by 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].

According to Shiramochi-ō, the shrine "flavor" is stated that as New Year's approached and those who celebrate the beginning of the coming year, to pray for a good harvest, and voice their aspirations this shrine was erected as a place so that the people's where wishes come to life. Currently, the deity that is expressed in the world is "Bishamonten". In a previous attempt to manifest in the world, there was an error when "someone" attempted to stabilize their existence. In its wake to form from the Sea of Possibilities, the shrine connected with the influence of one of the local gods, that being Warrior Takemikazuchi, thus creating the Takemikazuchi Shrine.

Mass for the Dead Arc
Momonga and his allies upon entering the Hatsumōde came upon a strange area in gold mist. Traveling through the dimension with their guide, Shiro, the group encountered many including some of the Floor Guardians and Pleiades under the spell of the "New Year's mood". After each encounter, the heroes claimed items that were somehow associated with the Seven Lucky Gods. They reached the 9th Floor where it was situated. There, the shrine stood. Cocytus was there acting as the gatekeeper and refused Momonga and his escorts entry unless they battled him. However when he was corrected by Shiro that the temple was no longer named the Takemikazuchi Shrine but the Bishamonten Shrine, he and the others in Momonga's party became confused on his words. Once Cocytus was defeated and awarded them the sansageki, Shiro explained that the shrine was a temple that was supposed to be dedicated to Bishamonten, one of the Seven Lucky Gods. And that as part of the location's event story, Cocytus was selected as its guardian due to his signature attack of [Acalanātha Strike], as in the literature Acalanātha or Fudō Myō-ō was a companion to the god Bishamonten.

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 Bishamonten 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. The shrine was almost an exact duplicate of the Takemikazuchi Shrine, save that it lacked the horn decorations.

Trivia

 * Bishamonten was the Japanese god of battle and one of the Seven Lucky Gods.
 * 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.