From Holtburg to Neydisa Castle, run to dungeon at 75.8N, 4.3E. OR From Mount Esper-Crater Village to settlement portals at 66.3N, 14.3E to Frosty Dale Cottages portal, run to dungeon at 75.8N, 4.3E.
One of three vaults that are part of the bur flagging quest. You need to retrieve the Ancient Ring with the description that contains the words: a sword ringed in purple fire, with the flames made of artfully layered amethyst shards. If you pick up the wrong one, there is a 15 minute timer before you can pickup another. The surface portal is tiable/summonable (useful if you are taking several characters or a large group).
The house golem will give you a note containing a quest hint if you retrieve the shard from the undead boss Vizidh the Despoiler at the end of the dungeon, however it is not required, you can just pick up the correct ring and leave if desired.