A Celestial Pill is an object of incredible value.
For it is something that only comes into being after the death of a Celestial Martial Realm King.
While a Celestial Martial Realm King is alive, a Celestial Gate forms within their Dantian. They use this gate to absorb immense amounts of Heaven and Earth Spiritual Qi, which they then convert into Magical Power.
Upon their death, the very essence of their life's Cultivation converges, crystallizing into a Celestial Pill.
This pill is also sometimes called a Relic.
However, only a Celestial Martial Realm King who dies a natural death will leave behind a Celestial Pill.
Take Xie Liuyun, for example. He and the Blood Demon King were annihilated together, leaving not even a body behind. Naturally, there was no Celestial Pill.
Generally speaking, a single Celestial Pill is enough to extend a Celestial Martial Realm King's life by a thousand years.
