Angor had been wondering about this problem as well.
Back in the royal palace, he tried using nightmare energy out of random and never expected it to work. Similarly, he was surprised and would like to ask Freud how this came to happen, but he decided to wait for later and discuss it in private.
"Mister Padt, was that your illusion energy?" asked Freud.
"You can say so." Angor nodded. Nightmare illusions were a special type of illusions after all.
"Was it the same illusion energy you used for building my room?"
Angor nodded again—he did use nightmare illusions to make the books and various furniture in Freud's room "real".
"Then I'm already seeing where to start the next course of my research!" Freud smiled. "Since you can activate the Dream Whelk, we'll be able to proceed from here and find out more. We just have to summarize our obstacles and solve them one by one."