The Spread Shot of Son Biten (a Touhou LW original). She attacks with mysterious divine power. Somewhere on the Youkai Mountain lies the Yamanba Sanctuary. Biten became an oni by eating the phantoms who ruled it. Before becoming a sarugami, i.e. a monkey who has become an oni, Biten was probably just a regular monkey or monkey youkai.

The Focus Shot of Son Biten (a Touhou LW original). She attacks with a mysterious weapon. Having turned into an oni, Biten believed she would descend into Hell, but she says the leader of the Kiketsu Clan, Yachie Kicchou, stopped this from happening. It was also likely Yachie who first put the idea into Biten's head that she was the reincarnation of the Great Sage Equal to Heaven. Perhaps it was this suggestion from Yachie that ultimately kept Biten out of Hell.

A Spell Card of Son Biten. This youjutsu attack resembles that of the Great Sage Equal to Heaven. Supposedly, the person who actually prevented Biten from ending up in Hell was one of its most powerful residents, Zanmu Nippaku. What's more, Biten devouring the phantoms who ruled over a certain land was part of Zanmu's plan to secure herself a spy to send to the Kiketsu Family.

A Spell Card of Son Biten (a Touhou LW original). This magical attack resembles that of a sarugami. It's clear that Biten is being manipulated by Zanmu. She was transformed from a regular monkey to a sarugami, which is a severe enough offense to garner a one-way trip to Hell. But Biten doesn't resent Zanmu―in fact, she's grateful toward her. Is that because all she knows about Zanmu is that she kept her out of Hell or because she knows that, thanks to Zanmu's scheming, she became far more powerful?

The Last Word of Son Biten (a Touhou LW original). She recalls her territory in this attack. The legend of the Great Sage Equal to Heaven states that they were born on the Flowers and Fruit Mountain before being trapped in the Marble Mountains. The legend also features many other notable mountains. In fact, it's fair to say the mountains play just as big a role in the legend as the Great Sage. While Biten was living on the mountain with all her monkey underlings, she surely spent a great deal of time thinking about the legend of the Great Sage (who she believed herself to be). She lived on the Youkai Mountain, i.e., the lost Yatsugatake Mountain Range. The Japanese symbol for "yatsu" is that of the sacred number eight and means "all." In other words, she lived in a place where all fantasy mountains gather.