Unique item

All artifacts are unique, but there are four objects which the game refers to as unique items (on the discoveries page):

• The Candelabrum of Invocation
• The Bell of Opening
• The Book of the Dead
• The Amulet of Yendor

While these are also commonly referred to as "invocation artifacts", they aren't actually artifacts; this also means they don't affect artifact wishing negatively as they don't increment the artifact count.

Artifacts are not unique items, as they are a normal type of item with a special name and additional benefits. For example, the Eye of the Aethiopica is a named amulet of ESP that also provides faster energy regeneration amongst other extra powers.

Stormbringer and the Tsurugi of Muramasa are the only runesword and tsurugi, respectively, that can normally be generated in the game, but neither count as unique items. It is, however, possible to find a non-artifact runesword or tsurugi in a bones file (if the artifact has already been created), or by wishing for one.