Draiss didn't kill anyone, simply making his way into the caverns, careful to move quietly before quickly, his invisibility and natural shadow bending of the night fury making him nearly impossible to see. He paused in the last cavern before the hostages, noting the locations of everyone, before he began carefully undermining the ceiling with spells, and working his way back toward the entrance, though only going into two different rooms before heading back. The spell was a magnified and modified shatter spell, which would work on almost any rigid, solid substance, not just a crystal, and would expand outward a bit. The three spells in each cavern wouldn't collapse the entire cavern, but it would definitely give the guards something to think about other than the hostages. He then slowly dispelled the invisibility, gradually becoming visible, but still clinging to the ceiling, hidden in the shadows of several stalactites eavesdropping for information.