This quest is similar to the earlier related quest, Rune-Warded Gate of Segrummar. This time you will need to find 5 ancient gears to open the door, as detailed here. Once all the gears are placed in the door mechanism, use the lever to open the door and complete the quest.
This guide for Dragon Age: Inquisition offers a detailed walkthrough of the main story and all side quests associated with each region, detailing easily missed features and hidden lore secrets along the way. The guide also covers all three main DLC: Jaws of Hakkon, The Descent, and Trespasser, and all dialogue choices throughout the game.
Inside this guide you will find:
Coming Soon! A detailed Character Builds section with coverage of all classes, skill trees, recommended armor, weapons, consumables, and much more!
A Walkthrough for all main story quests, detailing the consequences of your choices along the way.