The NetHack Wizard quest artifact. On defeating the Dark One, you will gain the Eye of the Aethiopica, which is an amulet with the following powers:

• Magic resistance (as per a cloak of magic resistance)
• Half damage from spell attacks
• Faster energy regeneration
• Gives telepathy while worn, as an amulet of ESP
• When invoked, the Eye will create a one-time portal to the closest level of any dungeon branch you have been to before. This will not work, of course, if you have the Amulet of Yendor or if you attempt it in the endgame levels.

In general, an amulet of life saving or an amulet of reflection are more useful, as you can be wearing only one amulet at a time.