Item sets are a great addition to Diablo II.  Even more collectible than uniques, Item Sets are fun, and very rewarding.  Though the individual items aren't of tremendous quality -- generally lower than Uniques, Rares, or good magical items -- they have interesting names, and if you manage to assemble a full set and equip it at the same time, there will be a bonus much greater than the sum of the parts.  (Or so it was said, with one set complete, the bonus turns out to be not so impressive.)

The two sets that have now been collected are the only ones that all items from it can be found in the beta.  All other sets have an item that is of a base type unfindable in Act One, so no other sets will be completed, unless other base items are changed, as the Angelic Mantle was.

"Item set" refers to the whole set.  Civerb's Vestments, for instance, which is comprised of a scepter, shield, and amulet, is one Item set.  The individual items in a set are referred to as "set items".  When dropped by monsters, these items display their names in green text, and all have unique names.  Set items are unique, in that they have pre-set stats, custom to each item, and non-random.  Only the AC and durability of set items can vary, just as it can for all other base items in the game; the names, various modifiers and bonuses, and item types for set items are fixed in stone.  One Angelic Sickle will be identical to every other one, aside from slight variations in durability.

There are said to be at least twenty item sets in the game, each with a different custom theme, and made up of three to six items.  The sets vary widely in components, and there are no set parameters.  Each set doesn't necessarily have a weapon, or a ring, for example.   And if you are wondering, there are some sets that have no overlapping items, so yes, it will be possible to wear two full sets at a time, though assembling the requisite pieces will be an incredible task.

Adding to the fun, item sets with more items are more powerful than those with fewer.  So a three item set, like the Civerb's Set, would (generally speaking) be much less powerful than a larger set, such as the four item Angelic Set.

Another interesting aspect of set items comes from guessing what the component items might be from the names.  Most have odd item names, such as "trim" or "guard" or "touch," where the actual item type is unclear. They are even outright confusing; the "Angelic Sickle" is a sabre, for example, rather than a "sickle", a type of polearm like a scythe.

Another nice aspect of Item Sets will be the community involvement of working to collect them with friends or guild mates, and of course trading them.  With over twenty item sets in the game, and an average of four or five items per set, there is no way one player will be able to store them all.  Guild Halls don't even have that much space, and certainly you couldn't carry many more than half a dozen set items on your character, even if you were wearing some of them.  There isn't that much space in the stash, and you'll need to carry extra equipment to use, so hard choices will need to be made about what to keep and what to sell or trade.

   

   Arcanna's Tricks
   Arctic Gear
   Berserker's Arsenal
   Cathan's Traps
   Civerb's Vestment
   Cleglaw's Brace
   Death's Disguise
   Hsarus' Defense
   Infernal Tools
   Iratha's Finery
   Isenhart's Armory
   Milabrega's Regalia
   Sigon's Complete Steel
   Tancred's Battlegear
   Vidala's Rig