Deep inside the castle, located at the top of one of the towers, was the Succubus Queen's chamber. Here was where the Succubus Queen rested and fed on the energy given to her by many other Succubuses who lived around the outskirts.
As their Queen, Lilith didn't need to go to find the Spirit Power to sustain herself. Indeed, she needed to find it herself if she went out to the outside world. But here, in the Underworld, her Spirit Power could be said as unlimited.
That was why Ao and the others didn't confront her directly, even though they knew they were stronger than the Succubus Queen.
And that was why Lilith stopped when Shuten Douji stepped in because the Succubus Queen knew the Oni God would spare no effort to destroy her castle and the surrounding area, rendering her unlimited supply of energy useless.
