Jibblinplip's lair was its own massive, bloated body.
"The only way to kill Jibblinplip is to find that single, original mote of ooze. It is in the absolute heart of the creature. Tear it out, then banish it to whence it came," said Sebastian.
"Banish it? Can't we just kill it?" The Princess asked while the armies took the front, checking for traps.
Sebastian shook his head. "It can't be killed in this plane. It'll just reduce to a smaller size that the naked eye couldn't see and escape for its life. It would just consume everything again and we're back to square one."
"But how do we banish it? No one knows what magic circle those wizards used or what spell they cast to conjure the monster."