In D2:ED there is a ten piece equipment set in each of the fortresses for Stone (Archmage set), Raze (Hunter's set - ranger) and Kali (Scorpion set - warrior). If you mindread those three bosses, as well as Xanlosch (in Stone's fortress), you can collect the four piece Ulthring's set.
Here is a map
showing the rough locations of the archmage set, or from the walkthrough
The archmage set is relatively popular for mage characters, and some people also like Ulthring's set since it allows more flexibility in other equipment choices. At least playing a strength based dual wielding warrior, I found my looted and purchased equipment better than the warrior set.
In DKS the set pieces were moved around, and additional sets were added.