"mm.." He made a noise as he looked up at her, feeling a little dumb as she seemed so familiar with the spell as if it was common knowledge. "Yet..." He rose his brows giving a half amused look that eventually turned into a little smile. " If I fall because my legs turn into.... whatever- your carrying me..and my axe.. I hope you got your magic for that too.." He continued on through the hallway that was soon filled with a water thick air. All the while he kept his eyes swishing from side to side and downwards to watch his step. "Animals.. that's right, i forgot about the venom of serpentine things- good point." And then the mention of a giant white worm made him cringe and he had to give a look at Cassandra. " A what? A giant.. white worm? what the- .." He imagined something like a large maggot or a large grub that the birds find in trees. These things were all that he could have to try and imagine what a creature like that would look like high up in the mountains. " I think i'd feel more secure if I didn't accidentally burn a hole in my armor..this is not cheap.." he said a little insecurely. 

Still though, he thought about what it could be like to have that acid on his weapon. He could tear away the armor of any opposing knight with it. " Hm.."
After a small while De noticed that she had gone silent and he gave a quick glance back again. She had a hint of somberness mixed with that '1000 mile long stare' they call it. Its a distant look that some of the soldiers get after killing their first man. De had it too, but you get used to it. 
But the slight somberness gave more of the impression that she was reminiscing rather than psychologically compromised. He thought of saying something,but decided to leave it be if she did not want bring it to light. They had just met some few hours ago, but its good to make quick friends especially before having a first battle. It helps ease the mind knowing that there is someone out there who has your back. 
So with out another word he decided down the staircase into the abyss.