This instance of Cauldron Hollow is accessed by looting and examining an old key dropped from owlbears and neriak crabs, or maybe any other mob in the zone from a small chest. It gives you the quest The Witch's Key which is finished by clicking on the Cauldron Hollow door and selecting The Witches' Cove.
Master D'Vaen, a level 25^^^ Dark Elf with two friends and a very large agro range.
Kabaner, a level 24^^^ skeleton with two friends (can be up in more than one spot in the same instance).
Shivantris the Wailing, level 25^^^ wraith with two level 25 wailing spirits