Mirkwood
One of the Teleri kingdoms that lasted the longest in time and would play an essential role in the fall of Sauron.
The relevance of Mirkwood in the history of Middle-earth gained importance over time, although always for specific moments rather than for sustained dominance or significance over the centuries.
However, some of its most important moments were key to Middle-earth.
It was the most giant forest ever known, dating back to the earliest times. Although Mirkwood lost its extension like other forests, its size was such that crossing it required several days of travel.
It was located throughout the northeast of Middle-earth, specifically in most of the region of Rhovanion. It was framed between the Grey Mountains to the north, the Brown Lands to the south, Rhûn to the east, and the Anduin River to the west. Within it could be found two more rivers running through it, a mountain massif, and several particular places that exemplified the vastness of the forest.
Mirkwood was not the first name the forest had. It acquired that name during the Third Age, when a dark Shadow settled over much of the southern area, and thus changed its name. Before, however, it was known as Greenwood the Great.
The arrival of the elves in Mirkwood most certainly occurred during the Years of the Trees, specifically when the Great Journey took place. Then, a Teleri group decided not to cross the Misty Mountains and entered the forest. They became the first inhabitants and founded a kingdom in the northeastern part of the forest itself.
From that moment on, they stopped being called Teleri and became known as Wood-elves, Silvan, or Nandor. Oropher was their first king. Many years later, some Men would come to live near the western edge of the forest, known as Woodmen and Beornings (two different clans).
The years would pass without significant events beyond quarrels with the orcs of the Grey Mountains and skirmishes with men of Rhûn (who were, however, more interested in the southern lands of Middle-earth).
Everything changed in the Third Age.
Much happened in a very short time in the eyes of the Elves.
After fleeing to the east when he was nearly destroyed at the Battle of Dagorlad many centuries before, Sauron began scheming to return to his plans to conquer Middle-earth. His strategy included Mirkwood (which at that time was still called the Greenwood the Great), where he built the fortress of Dol Guldur to control the entire northern area east of the Misty Mountains.
He disguised himself as a Necromancer so that no one would discover his true identity and intentions, and it was at that precise moment the forest was renamed Mirkwood. For around Dol Guldur, the trees became dark, the waters dark, and the animals disappeared.
The Nazgul began to frequent the area, and the Elves decided to move north with their king Thranduil, son of Oropher. So do the Woodmen, who leave the thicket, move to the northeast, and find Esgaroth on the outskirts.
Again a period of relative calm set in, which lasted several centuries until a surprise appearance stirred the waters.
A hobbit named Bilbo Baggins, the dwarf prince Thorin and twelve other Dwarves went into Mirkwood on their journey to the Lonely Mountain, located very close to Esgaroth. The group got lost and ended up being captured by the Wood-elves. Thranduil imprisoned them in his palace, and while he was deciding what to do with them, the prisoners escaped.
This event had a second part weeks later when Thranduil and his subjects took part in the Battle of the Five Armies at the gates of the Lonely Mountain, the first time in a long time that they left their kingdom and took part in external events.
In those same years, Sauron was expelled from Dol Guldur. Sadly, the entire southern Mirkwood remained a cursed and shadowy place. Though its foundations did not fall, it became the abode of three of the Nazgul.
During the War of the Ring, the Wood-elves could not stand aside, as all the free beings of Middle-earth had to fight to avoid falling under the dominion of the Dark Lord.
Under Thranduil’s command again, they helped their Lothlórien relatives, besieged by Dol Guldur’s forces in an all-out offensive by Sauron, who also attacked Minas Tirith.
When Sauron was finally defeated, Dol Guldur was destroyed by Galadriel. Thanks to this, the Black Forest recovered a name similar to the original: Greenwood or Eryn Lasgalen. The central part was given to the Woodmen, while the south, now free from the threat of Dol Guldur, became known as East Lórien.