In game terms, the actual effects and powers of possessing and/or wearing the Amulet of Yendor are as follows:

  • Casting spells will drain your energy faster
  • You suffer increased hunger
  • Your luck timeout will be increased
  • Monsters generated will depend upon the deepest Dungeon level you've reached, rather than the usual calculation of your experience level and the current dungeon level
  • Monsters will be less likely to be asleep
  • Level teleport will fail
  • The Wizard of Yendor always knows where you are
  • You gain clairvoyance, as the spell
  • When you try to go upstairs in Gehennom, you might teleport down 1 to 3 floors instead (this is extremely irritating)
  • When worn, you'll get messages that the amulet is getting "hotter" as you approach the portals in the endgame levels
  • The Wizard of Yendor can teleport or level teleport to come kill you
As you can see, possessing the Amulet is pretty much a bad thing. Don't wear it -- wear your Amulet of Life Saving instead, 'cause you'll probably need it.