This event was written and run by Stacey Allen. It was designed to be a covert mission - more of a seek and destory than a hack and slash.
Background: The country of Arstarr has been governed by a long line of lawful good kings who have undertaken a serious campaign to eradicate evil within its borders. They have had all known criminals relocated to Yan-Ka, an arctic wasteland to the north inhabited by goblinoids and the like. There are only three easy ways to get across the border, and the kings have had forts built in these locations as the major line of defense. In the last twenty years or so, the fronts have been very quiet; therefore soldiers serving at the forts have been somewhat complacent.
Death from Above: On a stormy night Fort Hellsbane is attacked. Enemy mages cast Stoneskin, Fly, and Feather Fall on some of their best champions. Those with Fly just flew over the walls. Those with Feather Fall and Stoneskin were catapulted over the walls. The unsuspecting occupants of Fort Hellsbane were quickly overrun and most were slaughtered. (The players were initially given soldiers and played out the attack - all of them were killed, as we intended. This is an old trick that helps throw the players off their stride and get the blood pumping early - we highly recommend it).
The Mission: A group of six veteran heroes (10th to 12th level) were to sneak in through the garbage pit (which is occupied by an otyagh). They were to find the leaders and dispatch them quickly and quietly, then get out. All of this is to prepare for an all-out assault come dawn. The players had a map of the buildings inside the fort, but know that the enemy may have converted structures to their own liking. The occupied fort is heavily patrolled and very dangerous. The characters wore light armor (leather or padded), if any, so to make as little noise as possible.
One thing we learned from this event was that not all people are accustomed to stealth and subtlety in AD&D. Of the four groups that played in the event, only two were successful (the other two groups were killed, at least in part because they weren't stealthy enough).