C991 The Muzzle of the Gun at the Back

"This is no ordinary crystal."

Lin Yu guessed.

The crystal here was definitely something he had never seen before. Inside the crystal, even the toughest of rutile would leave a mark if he pressed on it, but the crystal here did not exist. Just this was already amazing enough.

This confirmed Lin Yu's guess more and more, but he didn't stay any longer. After testing the toughness of the crystal