Deep in the passage, it was so dark that one would not even be able to see one's own hand. However, Merlin was probing his surroundings with his Mind Power at all times, so even though it was pitch-black all around, he was still able to "see" everything.
In front of Merlin, Wizard Riesen was practically on all fours as he cautiously moved forward. His Alchemy Creature was following behind him.
Merlin knew very well that Wizard Riesen was also guarding against him. Otherwise, if Merlin had wanted to kill Wizard Riesen in such a dark, narrow passage, Wizard Riesen would have no way of defending himself without the protection of his Alchemy Creature.
"We're here!"
Wizard Riesen gradually slowed down his steps. He turned around and said to Merlin in a low voice, "Wizard Merlin, don't use your Mind Power to probe ahead or you might startle the guardian."