Wind knight told Jack that the demon was a general of the burning army.
His name was Catlow. He could summon hounds and bats from the hell.
Wind knight also told Jack that only the purest holy light could eliminate the demon.
Although Jack possessed the power of a holy knight, he was not the real holy knight. He was unable to activate the power of the holy knight.
To seal demons, one had to pray the God.
"Take me there to have a look. Or maybe I have a way to deal with him. I promise you that I will never pull out the spear of Titans without 100% certainty!"
Jack pleaded.
"I believe you, young holy knight!"
Then he led Jack into a cave.
The spear of Titans was right in the cave. It nailed a demon against the wall. With his eyes closed, the demon's heart was pierced through by the spear.
To see the true face of the demon, Jack took a few steps forward. But when he stopped, he heard footsteps from the cave.
"Someone is coming. Let's hide first!"