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.
Faxanadu (J)
Type: PRG0
Label: HFC-FX-0 PRG
Size: 256 KB
CRC32: A80FA181
x!: 1