<span class='standouttext'>Spoiler : </span><span class='spoiler'>There are three components that you need: Coal (in the room where you killed Fergus),Salt(from the Kitchen with the cook who had the rat problem)and Sulfer (in the Medical Officer's room). First combine the salt and the coal in your inventory this will make a new barrel, drop the sulfur on that mixture to make an explosive. use your mouse to highlight the forge lava (right over the lever) and drop the explosives on it. Result- bye bye Citadel and you get 22,000 XP's for your troubles.</span>
