Identify which bytes are used during battle for HP Drain and MP Drain.
Create a new subroutine in the game to allow MP Drain digits to offer a new color, versus HP Drain.
There are 5 ways to drain MP in the game:
The two Mix recipes are almost certainly different in a lookup table, but it’s uncertain if they point to the same effect routine in the rom.
Using an editor (ff6tools) I made a single change to this ability, in order to find where the code is located in the rom.
Changing it from “Drain MP” to “Drain HP” modified the byte at $110F4C, and I’ve reason to suspect this is the 5th byte in the routine based on the editor’s UI.
These are the 8 bytes centered around this offset, and you’ll see that a pattern of 8 bytes is common in in the other battle effects.
38 04 00 80 0E 80 08 00
This helped demonstrate that the value $0E represents “Drain MP” and became $0D in my tweak with the editor.
Notice how the last 2 options in the editor have the values 8 and 0, and how the last 2 bytes in this series are $08 and $00! (If you use a calculator, you can see that $80 is actualy hex for 128, too…)
Here is a snapshot of the FFV rom while HP Drain is happening in battle from the first part of the DrgnSwd Ability.
Bytes utilized for this effect are $110F08 - 110F17.