LOTS OF SPOILERS AHEAD...
See topic. Which area do you think has the most useful items, with the best risk/reward factor?
For me, its a tie between the Astral Prison and Watcher's Keep level one.
The Astral Prison is chock-full of goodies: Boots of Speed, Kundane, Adjatha the Drinker, the Staff of Air, the Wave Shaft, Melodic Chain, Pixie Prick, the Cloak of the Shield, the Gauntlets of Weapon Skill, a Ring of Protection +1, 3 Star Sapphires (for upgrading the Dagger of the Star) and some nice scrolls and gold.
W.K. level one contains some extremely useful items, especially for Archers: the Ammo Belt, Case and Quiver of Plenty, the Crimson Dart, Darts of Wounding, and some generally useful items: Usuno's Blade, Foebane, the Flesh Golem manual, Paladin's Bracers, and some gold.
That, and WK has two of my favorite items sold on top...Firetooth and the Short Sword of Mask