But ever the shadow in Mirkwood grew deeper, and to Dol Guldur evil things repaired out of all the dark places of the world; and they were united again under one will, and their malice was directed against the Elves and the survivors of Númenor. ~ The Silmarillion, Of the Rings of Power (Art: “Dol Guldur” by AndrewRyanArt on DeviantArt)