Dararoth was the last great dragon of Middle-earth. Before the fourth-age he slept undisturbed, before the over-curious elves of Eryn Lasgalen began expeditions into Mountains of Mirkwood, where Dararoth slumbered. Angered when Thranduil's elves invaded his lair, he struck back at them, killing a dozen of their number.
The elves then treated the mountains with caution, and no elf set foot near Dararoth's lair again. However, The Castellan, attempting to nuture the dying flames of what was once Sauron's army in Mirkwood, was quick to contact the dragon, whom he hoped would share a common goal in destroying the elves.
However, the dragon was not as charitable as the Castellan had hoped, and attacked the emmisarries he sent to Dararoth's lair. The Castellan, dissapointed, but not yet beaten, sent a second group of ambassadors, this time bearing gifts for the creature. However, the visit was as distatarous as the first.
After failing twice the Castellan became increasingly angry, even going as far to contemplate killing the beast. However, he disgarded that plan, and formed another, even craftier one.
During the Plundering of Dol Guldur, the Castellan uncovered one of the Nine Rings gifted to the kings of men by Sauron. He had been hoarding it atop Taur Ungol, but he now considered it in his plans. By playing on the dragon's weakness for treasure, the Castellan promised Dararoth the ring, in return for his co-operation.
Dararoth, though a cunning and intelligent creature, had little choice but to accept the offer. However, his services where limited to those in the Black Fortress, and the dragon did little to aid the war against the elves.
However in 20 FA, Dararoth was called to aid in the Battle of the Old Forest Road, where he was slain by Thranduil.