As some might have guessed. Muku was forcibly searching through Nightmare's soul for the information he needed.
This was of course extremely painful to Nightmare.
And it wouldn't have been possible if its soul wasn't as damaged as it was. Even if it was trapped in Muku's mindscape. Unfortunately, it was hurt enough to allow for such a thing to happen.
In no time at all Muku was done with the search. He didn't learn anything else because he ignored it not wanting to learn things that could complicate his life like he always does.
After that, he pulled out and looked at the weakened Nightmare with a smirk on his face then...
He opened his mouth wide. It also grew in size as he did so until it was around five times bigger than it normally was.
This was of course only possible because it wasn't his physical body he was using so there were no physical limits.
After that, a strong suction force started coming out of it. Then Nightmare began getting pulled into his mouth.
