Are you referring to the portal stone 2 rooms north of the room with the crystal fragment, on the western side, which teleports you to the wisdom dungeon? Other than the wisdom rune (which teleports you back to the fifth level of the catacombs), the only things of interest there are a random charm, a trapped chest with random loot and the third book teaching the Raanaar language.
You may not be able to return there once you have found the wisdom rune. After clicking on the first few symbols on the wall, I cleared the rest of the area before going through again to find the rune.
