Breath of Fire II/ROM map

The following ROM data was obtained from an old Gamefaqs thread (link) by a user called StarryKnights.

Characters starting information

Initial data for the game's characters. Information block starts at x00:087C ($C0:087C) and ends at x00:0D3B ($C0:0D3B) (Assuming no header). Each entry is 64 bytes long. Layout:

1-4: Character Name
5-6: Unknown, 00 for all.
7: Character's PC Number
00 - Ryu
01 - Bosch
02 - Rand
03 - Katt
04 - Nina
05 - Jean
06 - Sten
07 - Aspara
08 - Deis
09 - Kid Ryu
0A - Kid Bosch (Zombie in battle)

8: Initial level
9-10: Unknown
11-12: Initial HP
13-14: Unknown; always the same as initial AP. (Possibly Unused)
15-16: Initial AP
17: Character portrait/sprite modifier; 00 for everyone
18: Initial Strength
19: Initial Stamina
20-21: Initial Agility
22: Initial Condition
23-24: Initial Weapon (Value 11 tells the game that you have a weapon equipped)
25-26: Initial Shield (Value 21 tells the game that you have a piece of armor equipped)
27-28: Initial Armor (Value 21 tells the game that you have a piece of armor equipped)
29-30: Initial Helmet(Value 21 tells the game that you have a piece of armor equipped)
31-32: Accessory Slot 1; If you unequip the item makes it unable to be equipped. (This is a natural bug)
33-34: Accessory Slot 2; If you unequip the item makes it unable to be equipped. (This is a natural bug)
35-43: Unknown; from what can be understood, it would be the attack, defense, vigor stats. (Unused)
44: Initial Guts
45: Initial Wisdom
46: Initial Luck
47-49: Initial EXP
4A-64: Unused

There are three sets of characters in this data block. The first set is for the normal game, for the most part. The second set consists solely of Child Ryu and Child Bow. Adult Ryu (Maybe Adult Bow too) inherits his stats from Child Ryu. This is only worth noting if you want to change his starting stats.

The third set is what I can only surmise are the team's stats during the title screen demos.

Stat gain tables

Stat Gain Tables:
----
Hex offset (LoROM Address)
x05:71B0 - x05:5DEF ($C5:71B0 - $C5:5DEF)

4 bytes, split into 8 half-bytes in this order with a max increase of '15 (F)' per stat: 

Byte 1: HP, AP
Byte 2: Strength, Stamina
Byte 3: Unused, Agility
Byte 4: Wisdom, Luck

Almost every character seems to have extra level gains for levels they don't join at. These are not used at all due to the initial data. <br/>Also, it seems Bleu's stats uses the Monster Table as her level up data so she doesn't have her 'own' to modify without some serious stat table moving.

Guts gain upon level is consistently the same for every level up.  Each PC's gain starts at: 
x01:8FE5 ($81:8FE5)

Enemy information

Enemy stats:

59000-5A8FF

Bytes 1-8: Name

9-10: Hit points

11-12: AP

13: Luck

14-15: Attack

16-17: Defense

18-19: Agility

20: Drop rate???

21-22: Experience

23-24: Zenny

25: Item set

26-32: Unknown

For detailed information on how drop rates and item sets work, check out Ben Siron's handbook that explains many of the game's mechanics: link

Spell gains table

Pointers: 5AA00-5AA011

5AA12-5AADE

Pairs of bytes. First is for level the spell is gained on, the second is the spell gained. 00 terminates.