A shade is an undead creature, created by black magic.
It cannot be harmed except with blessed or silver objects, magic, or artifact weapons with a damage bonus. Orcus Town is the only place where shades appear. If you've gotten this far without an alternative, you can use the Bell of Opening as a silver weapon against them. Unarmed gloveless combat with a silver ring equipped can also work, as can unarmed combat with blessed gloves (although this is very slow.)
Shades can also move freely through solid rock, and can see invisible creatures.
Shades are undead creatures. They differ from zombies in
that a zombie is an undead animation of a corpse, while a
shade is an undead creature magically created by the use
of black magic.