Lake of the Staff of Two Heads

The Lake of the Staff of Two Heads is an additional location hidden not far from Tōga's tomb in the Border of the Afterlife, which also happens to be connected to, as its name suggests, Jaken's demonic mystical Staff of Two Heads as well as the Realm of Fire. It is a lake of clear water surrounded by fire. From there, Inuyasha and Kagome were able to keep taps on Moroha as she grew, thanks to Jaken using his staff to project images of their daughter onto the surface of the lake.

It is also where Inuyasha finally realizes that the only thing that can grantee their return to the physical world is Tenseiga being called by Towa's connection with her father's powerful healing sword. It is also, where they learn of Kirinmaru's ultimate goal upon reaching the modern era: which means the Grim Comet is coming in full and will obliterate humanity.

Trivia

 * It is the third immaterial place that is directly associated with death and its varied nonphysical realms such as, , and even  itself.