The Lord of the Rings without treading on his toes and ripping apart the world. It is also the subject of the exploring Middle-Earth column over at the Europe LotRO community.
"The folk of Middle-earth's northern lands have long held the name of Angmar in dread, but in that fell kingdom are places that cause even the minions of Mordirith to tremble. At the feet of the Mountains of Angmar lies the terrible land of death and decay, Gath Uior. Even the Orcs and evil Men who gather there fear what lurks behind the great portal that leads under the mountains. It is said that ever-vigilant guards watch the gates, which were hewn long before the Witch-king first came to Angmar – not to keep enemies out, but to keep something in."
If you wish to check out the full article, jump on over and look at the neat screenshots and all of the lore of the Rift in one location.