The mass of Essence Energy they were referring to was the very same ball of pure energy produced when Li Chang'an's Soul Fire incinerated the Sun Emperor.
At the time, Li Chang'an had been afraid his Soul Fire wouldn't be able to completely purge the Dark Energy, so he hadn't absorbed the flame directly. Instead, he had stored it in a relatively safe location, planning to take the time to study it thoroughly later on.
Upon closer study, Li Chang'an discovered that the energy mass did indeed contain a considerable amount of Dark Energy. If he absorbed it, he would very likely become a new host for the Dark Energy, just as the Sun Emperor had. Thus, the matter had been left unresolved ever since.
He never imagined it would end up attracting the attention of the Liyang Imperial Fleet today.
