This patch is by Unsavory Maggot, and works on any version of Faxanadu for the NES.

In the original game, the pendant reduced attack power by 25% -- this is because the pendant is "in effect" when you don't have it. To clarify, it was a simple mistake, and a quick fix -- changing a BNE to BEQ. Now you don't start with the pendant effects and lose them when you pick up the actual pendant; you have the effects when you have the pendant!

The address for the bugfix is the same for all versions, so patch whichever version you'd like.