Cameo Fantasy III

I'm so excited for this project, sounds fun! And I've been waiting so long for Djinn to release lenneth's sprite sheet :p

I can barely read cause I'm so asleep, but I did notice you want to redo the damage from Regen/Poison. The code to do that (including the damage/recovery formula) is given here:

Regen and Poison

C2/500B: AD 77 3A LDA $3A77
C2/500E: F0 CF BEQ $4FDF (Exit if $3A77 = 0)
C2/5010: B9 A1 3A LDA $3AA1,Y
C2/5013: 29 EF AND #$EF
C2/5015: 99 A1 3A STA $3AA1,Y (clear bit 4 of $3AA1,Y. because we're servicing this
damage/healing request, we can allow C2/5A83 to queue
up another one for this entity as needed.)
C2/5018: B9 A0 3A LDA $3AA0,Y
C2/501B: 89 10 BIT #$10
C2/501D: D0 C0 BNE $4FDF (Exit if bit 4 of $3AA0,Y set)
C2/501F: 20 8A 29 JSR $298A
C2/5022: A9 90 LDA #$90
C2/5024: 14 B3 TRB $B3 (Set Ignore Clear, and allow for damage increment
even with Ignore Defense)
C2/5026: A9 12 LDA #$12
C2/5028: 85 B5 STA $B5 (Set command to Mimic)
C2/502A: A9 68 LDA #$68
C2/502C: 8D A2 11 STA $11A2 (Sets to only ignore defense, no split damage, reverse
damage/healing on undead)
C2/502F: 4E A4 11 LSR $11A4
C2/5032: A5 B6 LDA $B6
C2/5034: 4A LSR
C2/5035: 4A LSR
C2/5036: 2E A4 11 ROL $11A4 (Set to heal for regen; damage for poison &
seizure/phantasm)
C2/5039: 4A LSR
C2/503A: 90 15 BCC $5051 (Branch if not poison)
C2/503C: B9 24 3E LDA $3E24,Y (Amount to increment damage)
C2/503F: 85 BD STA $BD
C2/5041: 1A INC
C2/5042: 1A INC
C2/5043: C9 0F CMP #$0F
C2/5045: 90 02 BCC $5049 (If under 15)
C2/5047: A9 0E LDA #$0E (Set to 14)
C2/5049: 99 24 3E STA $3E24,Y
C2/504C: A9 08 LDA #$08
C2/504E: 8D A1 11 STA $11A1 (Set element to poison)
C2/5051: B9 40 3B LDA $3B40,Y (Stamina) (Figure damage)
C2/5054: 85 E8 STA $E8
C2/5056: C2 20 REP #$20
C2/5058: B9 1C 3C LDA $3C1C,Y (Max HP)
C2/505B: 20 B7 47 JSR $47B7 (Max HP * Stamina / 256)
C2/505E: 4A LSR
C2/505F: 4A LSR
C2/5060: C9 FE CMP #$00FE
C2/5063: E2 20 SEP #$20
C2/5065: 90 02 BCC $5069 (If under 254)
C2/5067: A9 FC LDA #$FC (set to 253)
C2/5069: 69 02 ADC #$02
C2/506B: 8D A6 11 STA $11A6 (Store damage in battle power)
C2/506E: BB TYX
C2/506F: 4C 67 31 JMP $3167

What you may want to take a look is the "Jump to Subroutine" command
C2/505B: 20 B7 47 JSR $47B7 (Max HP * Stamina / 256)
Which sends you to C2/47B7 to perform multiplication and division.