"Infernal Heavens!"
One could light up the air with that Invisible Heaven Flames, and then burn everything within one's vicinity within one's control.
This was the most difficult step illustrated in the jade scroll.
The practitioner had to risk their lives finishing all the prerequisites, and then develop a sense of the spirits of all things around them before he could ignite something remotely.
Xu Xiaoshou closed his eyes and attempted to find that spirit inherent in all things.
He opened his eyes the very next second.
"What's happening?" he thought.
"I've finished the parts that require one to 'risk one's life,' yet why..."
"Is this 'sense the spirits in all things' so d*mn easy as well?"
He didn't even need to use Sense. He could easily perceive the spirit in all things in a fifty-meter radius just by using the sword intent needed to use "All Things are Swords."