The Eye of the Aethiopica

"   The Eye of the Aethiopica
Base item	amulet of ESP
Affiliation	neutral Wizard intelligent
When carried	magic resistance faster energy regeneration half spell damage
When worn	(none)
When invoked	branchport
Base price	4000 zm
Weight	20

The Eye of the Aethiopica is the wizard quest artifact. It is neutral for wishing purposes; if you are a wizard, it will adjust its alignment to your starting alignment.

Its base item type is amulet of ESP, so wearing it provides extrinsic telepathy. You can also abuse the naming artifacts exploit to determine whether an unidentified amulet is ESP or not.

You can invoke the Eye to branchport. In other words, you can immediately teleport to another branch of the dungeon that you have visited. You arrive on the previously-visited level of that branch which is closest to your current location. Attempting to branchport to the branch you are currently in gives the message "You feel very disoriented for a moment." and has no effect. Adjacent hostile monsters will follow you through the gate into the new branch; this is a common method to transport many wraiths from the Valley of the Dead so they are more likely to leave a corpse. The branchport ability of the Eye makes Sokoban an ideal stash location. A typical branchport menu might look like:

                                  Open a portal to which dungeon?
----------
|........-####      ------------- a - The Dungeons of Doom
|........|   #######-...........| b - Gehennom
|........|          |...........| c - The Gnomish Mines
----------          |..@........| d - The Quest
                    --------+---- e - Sokoban
                            #     f - Fort Ludios
                            #     (end)

When carried, The Eye provides half spell damage, magic resistance, and fast power regeneration. With fast power regeneration, you restore at least one power per turn -- this is far quicker than you would otherwise.

In the opinion of many experts (such as Rast and Eidolos), the Eye of the Aethiopica is not only the best artifact in NetHack, but also the best item.