Siege on the Dragon Cult

Walkthrough
This quest is initiated when the Dragonborn enters the courtyard of Forelhost and meets Captain Valmir. The Captain's story changes depending on the Dragonborn's allegiance (Stormcloak/Legion), but the thrust is the same: the captain asks the Dragonborn to enter the ruins and recover a powerful artefact, a Rahgot's mask, and bring it to him. He also mentions the potentially useful Skorm Snow-Strider's Journal left behind many years before.

Find Skorm Snow-Strider's journal (Optional)
Glass Claw,

Find the key to the well in the Catacombs (Optional) or Return to Valmir

 * If Captain Valmir is already dead, the objective assigned will be to find the key to the well in the Catacombs.
 * If Captain Valmir is still alive, then the objective assigned is to return to him with the mask.

Kill the imposter Valmir
Die Belagerung des Drachenkultes