Large portions of this article have been directly copied from the relevant Wowpedia article.
In the middle of Darrowmere Lake is a solitary island: the Isle of Darrow. "The keep of Caer Darrow, perhaps the oldest human monument in the world, stands upon this isle. The keep’s defenders abandoned it during the Third War." The ruin may hold many wonders, but unforturtunately it crawls with undead and their few remaining demonic allies, including at least three dreadlords.
The island where the ruined town of Caer Darrow now sits was long ago the keeping place of an ancient runestone, known as the Runestone of Caer Darrow. The runestone served as an ancient monolith sacred to the high elves of Quel'Thalas. The artifact is said to have been erected by elven druids, a description which provides the only indication in lore that any high elves ever followed a druidic path. Runestones were later changed to have served as a barrier so that the Burning Legion would be unaware of the high elves' arcane magic.
The island has also been the site of one or more human fortifications dating back to the days of the empire of Arathor.
The Second War
During the Second War, the island was invaded by the Horde, the fortress sacked, and the sacred runestone captured. The stone was hewn into pieces which were used to create the Altars of Storms, arcane structures which allowed Gul'dan to instill magic into the Horde's ogre allies.
When Uther the Lightbringer embarked for the isle on a mission of mercy to aid and comfort the survivors of the bloody raid, he was ambushed by privateers from Alterac. In the naval battle that followed, some of the sailors were captured; during questioning in Lordaeron's capital, they confessed their nation's treachery to the Alliance, leading to Alterac's eventual ruin.
The Barovs and Scholomance
Following the Second War, the fortress at Caer Darrow was restored; the rule of the island by the Barov family dates back to at least this time. The Barovs were extremely wealthy, owning the land which comprised Caer Darrow, Brill, Southshore, and Tarren Mill. Not content with their enormous holdings, the Barovs entered into a deal with the human mage Kel'thuzad, leader of the Cult of the Damned. The once opulent House of Barov became the horrific Scholomance, a school of necromancy. The spirits of many of the island's inhabitants remain, seeking justice for the horrific wrongs committed there.
Fall of the Town
The people of Caer Darrow survived within their small town for several months after the fall of Lordaeron. When the Scourge invaded Andorhal however, a large host attacked Caer Darrow. Aided by troops from Scholomance, it was then that the town finally came to an end.
The island and surrounding lake have become lifeless and still. Only meager fish are still able to survive in the murky waters and the towering fortress seems to suck hope itself from the surrounding air. Every year or so new students can be seen entering the manor, or graduates grimly sulking out. Only ghosts of the town's former inhabitants remain, only visible with the spectral essence given by the manor's former servants. The townspeople seem to be cursed to re-live Caer Darrow's happiest day for all eternity, the visitation of Uther the Lightbringer. As of the late evening of August twenty fifth, the Darrow has since been occupied by a Forsaken force known as the Black Brigade, along with their leading 'Riders of Vengeance', and accompanying Necrolord. (Search 'New Vengeance Landing', for futher information regarding the keeps current standing.)