The model I've chosen is something similar to the Angband edit file, with a few modifications. Here is the template:
# Each creature has an individual entry in the following format:
# N: ID : singlular name : plural name
# L: Creature Level : Rarity : Uniqable?
# E: Ecology : Type: Pickup Items?
# G: Display Character : Display Colour
# I: Hit Dice : Armour Class : Evasion : Speed
# V: Initial Alertness Level
# A: Action Frequency : Action Text
# S: Speech Frequency : Speech Text
# B: Attack Method : Attack Effect : Damage
# M: Spell | Spell | Spell | etc
# F: Flag | Flag | Flag | etc
# C: Class | Class | etc
# D: Description
Anyone familiar with the Angband source should recognise most of these options, although I've enhanced a couple, and added a few additional sections.
Below I give a couple of excerpts of 2 creatures already in Kharne translated over to the new format:
N: 2 : Kobold : Kobolds
L: 1 : Common : Yes
E: Fortress: Goblinoid: Yes
G: k: $004080
I: 1: 5: 11: 12
A: 10: "picks a chunk of rotten meat from its teeth"
A: 10: "yips noisily"
S: 20: "I'm gonna kill you! Yip yip!"
B: HIT: HURT: 1d6
B: SHOOT: HURT: 1d6
F: COWARDLY | FLEE | OPEN_DOOR | GREEDY
F: EVIL | POISONOUS | CORPSES
F: DROP_ITEMS_POOR | DROP_CASH
C: Commando | Archer | Lurker
D: "Kobolds are short, ugly goblinoid humanoids."
D: "They are known to have cowardly and sadistic tendencies."
N: 23 : Ogre Mage : Ogre Magi
L: 4 : Rare : Yes
E: Fortress: Giant : Yes
G: O: $FF00FF
I: 4: 6: 12: 12
A: 10: "waves a magic stick"
A: 10: "yells a magic word"
S: 20: "dis two and dat two make four, right?"
B: HIT: SLAM: 1d6
M: MAGIC_MISSILE | HEAL | HOLD | TELEPORT
F: RANGED | BESERK | OPEN_DOOR | GREEDY
F: EVIL | CORPSES
F: DROP_ITEMS_POOR | DROP_ITEMS_GOOD | DROP_CASH
D: "Ogre Magi are hideous and deformed ogres wrapped in deathly black robes"
D: "They are known to be cruel and masters of deadly arcane magics."