Gargoyle's Redemption
Gargoyle's Redemption was the name given to an EA-run scenario in UO, that took place from September to November of 2001.
In this scenario, the evil plans of Blackthorn and Exodus began to be discovered, and Central Ilshenar opened up. In the climax of the scenario, the characters helped to free the Gargoyle city of Ver Lor Reg by fighting a long, brutal battle in the Exodus Dungeon.
Lord British's court wizard Nystul played a major role in this scenario, building a device, with components contributed by the characters, that dropped the shielding that had hitherto covered the Exodus Dungeon.
That device is still found in-game, in the southern part of Castle Britannia in the Trammel facet, near the stable.
References
The Scenario index on UO.com is extremely useful: http://www.uo.com/cgi-bin/newstools.pl?Article=6616