The designers of the Bahraha’s Gloom did an excellent job hiding the dungeon skyshard. In order to reach the skyshard you will need to find the entrance to the secret passage leading to the upper plank walkway above the dungeon floors.
In the dungeon live a lich (Magnifico) that lies dormant until you kill his guardian. In the upper portion of this room (behind the boat wreckage), there is a passage that leads north. The passage will immediate turn west. Watch the north wall of this passage for a small break in the wall. It’s the entrance to the secret passage leading up to the wooden plank walkway in the ceiling of one of the large dungeon chambers. Continue heading west on this plank walkway until you find another cramp passageway up. Eventually, the path leads to the skyshard. There is a lever to access the main entrance room for a quick exit.