After a while, Matthew and the others emerged from the Secret Passage and arrived underground. There was only a narrow room here.
"Did we come to the wrong place? There's nothing here!" Jerry muttered.
"There's a pool of water here—" Luna pointed at the puddle in the center of the room.
"Professor Merlin, is the Castle Core in the water?" Matthew thought of the Goblin Secret Vault he had visited during the summer holiday. Its entrance had also been on the surface of the water.
Merlin stroked his long beard. "Indeed. It seems you know a little about Goblin Secret Vaults. Jumping into the water will let you enter the space inside."
"Eh—there really is a space in the water! I can see Goblins inside!" Jerry leaned closer. Instead of seeing a reflection, he saw an entirely different space within.
"You stay here and watch what's happening inside through the water's surface. I'll go in first." Matthew did not waste any time. After casting protective Magic on himself, he jumped into the pool.
After entering the pool, he did not feel himself getting wet. Instead, it felt as though the whole world had instantly turned upside down.
By the time Matthew came to his senses, he had already arrived in the room beneath the water's surface.
This place was far larger than the room outside. In the center stood a huge sphere of light several meters across—the core of Hogwarts Castle.
Beside the sphere stood a bald Goblin with his back to Matthew. One arm, clad in barbed thorn armor, was thrust into the sphere.
Matthew immediately felt that something was wrong. The sphere and the Goblin were enclosed within a round azure barrier.
Matthew tried waving his wand, and a beam of spell light struck the barrier, but it