These creatures had been slowly rebuilding their strength ever since the catastrophic end of the First Age killed so many of their kind. The problem is, the Grey Mountains happen to be located near to a barren waste populated by the great worms. In doing so, though, they once again run smack dab into a larger-than-life problem that no one could've predicted - dragons. Others migrate further north to the Grey Mountains, where they explore new lands and find hordes of previously untapped wealth. Many areas become abandoned afterward, and it soon becomes clear that Gondor doesn't have enough manpower to maintain its watch on Mordor any longer, opening up the doors for first the Ringwraiths and later Sauron himself to return to their ancient homeland. It kills the ruling king of Gondor and his children (yes, this is before the last king dies at the hands of the NazgГ»l), and then it spreads across the continent, devastating every region that it touches, including the hobbits of the Shire. It also states that the sickness 'came with dark winds out of the East,' going on to strongly hint that it coincides with a variety of other evil events that collectively point to a newly resurgent Dark Lord.ДЄs far as the Great Plague, in particular, is concerned, we're talking about an utter catastrophe - not just to the men of Gondor but for their enemies, their allies, and all of Middle-earth besides. In the appendix to The Return of the King, it explains that this pestilence is pretty much the 'greatest evil' that Gondor ever faces, which is a pretty big deal, all things considered.

Soon after the Shire is founded, a terrifyingly deadly plague arrives in Middle-earth.

Lord of the rings the third age guide