Sethekk Halls is a wing of the Auchindoun instance. It's geared for 5 level 67-69 players (although it will appear in the dungeon finder menu for level 65 characters). The entrance is on the east side of the Ring of Observance. It is populated by renegade arakkoa and led by the insane Talon King Ikiss. It should take about 90-120 minutes to complete. Soloing this instance is viable at 80 and the potential loot drops from it make it reasonably lucrative to do so. The achievement will also be granted on completion to those who do not already have it as well.