Monsters are invincible/Algorithm question???

Monsters and player characters use the same damage calculation for magical attacks, handled at C2/2B69. You can check the physical damage calculation at C2/2B9D to see how it handles calculating damage differently for monsters and PCs.

The X register usually holds the attacker ID, a number from $00 to $14, for each of the ten possible entities in battle. For PCs it is $00, $02, $04, or $06, so CPX #$08 and BCC is often used to differentiate between characters and monsters. For targets, the Y register is used instead.