This large shield of black metal bears a strange, twisting symbol on its face, done in some manner of relief. Anyone within 60’ viewing the front of the shield must make a save versus Magical Device or be affected by the symbol’s effect. (During combat, attackers get a +2 to the save because they aren’t concentrating on the shield as much as their opponent’s movements.)
Anyone failing the above save is lulled into a state of unconsciousness that lasts for 1d4 hours. Upon awakening, he or she has completely forgotten the events of the previous day. In cases where the subject has experienced severe mental trauma, this amnesia will cure them of any insanity or mental disorders caused by those experiences.
However, the shield also has a massive side effect: it emits microwave radiation in a 60’ radius. Water within 60’ of the shield begins to boil, and living things are wracked with pain as if they are on fire. The pain is so intense that everyone within 60’ of the shield, including the wielder, must make a saving throw versus Paralyzation in order to act normally. Those afflicted will usually either collapse or attempt to move as quickly as possible out of the radius. Creatures that roll a 1 on the saving throw against Paralyzation take 1 point of damage from blisters and surface burns.
Because both of these effects are permanent, the Forgetting Shield is usually stored in a strange basket of woven metal, and only removed by the strongest warriors. (This basket acts as a Faraday cage, in case any of your PCs get any brilliant ideas of what to do with that.)
This artifact works roughly the same way in any old school class-and-level RPG variant, but if you're using 5e, I'd check out the Symbol spell to help adjudicate the effects — Con save for pain, Wis save for amnesia/sleep. I'd set the save DC at 20, although you can set it at 15 if you're a generous soul. If you see the shield in combat, gain advantage on the Wisdom saving throw.
