NOTE: Following information taken word for word from Warcraft 2: Tides of Darkness manual.
THE RUNESTONE AT CAER DARROW
The Runestone was an ancient monolith erected by the Elven Druids and inscribed with powerful runes of protection and warding. The Runestone, seized by Gul'dan and his Ogres, was eventually hewn into slates that were then used to construct the Altars of Storms. The Elves, knowning that their sacred artifact had been defiled to create the Ogre-Magi, have sworn to destroy all of the unholy Altars across the kingdom.
THE TOMB OF SARGERAS
Buried beneath the Great Sea for over one thousand years, the ancient Tomb of Sargeras waits to be discovered by any foolish enough to pursue its secrets. The Tomb is rumored to house the remains of the ancient Daemonlord Sargeras, defeated in a contest of arcane mastery by the legendary Guardian Aegwyn. The sorcerer Medivh - scion of Aegwyn - promised to divulge the location of the Tomb to Gul'dan in exchange for the destruction of Azeroth. Before Medivh could do so, his tower was invaded and he was slain by the warriors of Azeroth. Gul'dan, believing that the Tomb contains power absolute, hopes to find and claim it as his own. Success may indeed make him a living god.
THE PORTAL
Encircled by a ring of towering obsidian stones, the Portal stands some fifty feet above the marshy ground of the Black Morass. Being the original gateway to Azeroth that was opened by the wizard Medivh before the First War, its constant use has increased it in both size and power. It serves as a passage to untold numbers of Orc and Ogre warriors, reinforcing the Horde's already overflowing ranks. The lands around the Portal that were once dead swamps have been transformed into barren soil the color of blood and are now teeming with strange, demonic beings. This dark perversion of the land is steadily spreading across the continent of Azeroth and threatens to consume the entire world.
NOTE: This is the Dark Portal in the Blasted Lands which was once the Black Morass.