Enemy Artificial “Intellgence”

Every enemy has, in its bestiary definition, a defined AI ID. Changing this does not actually have any discernable effect; I’m not sure why that byte is in the monster definition. I’m not arguing, because it provided me a clue as to how to find the following table: the AI IDs are found at 0×22f0b8 to 0×22f17a. This is a span of 195 bytes, so each monster gets exactly one byte. The bytes are listed in monster ID order, so you’ll need to refer back to the bestiary entry to get the listing for the various IDs.

It will be noted that the value 2c is plentiful. That’s because this value is set to “fight 100% of the time”.

AI Indices table, by Monster

To save you the trouble of figuring out what each ID refers to, I’ve got a handy-dandy chart showing the first monster to use each AI ID.

0×00	Winter Wolf	Fire Lizard	Basilisk	Big Eyes
0×04	Deep Eyes	Hellhound	Ogre Mage	Sand Worm
0×08	Evil Eye	Death Eye	Rakshasa	Vampire
0×0c	Vampire Lord	Horned Devil	White Dragon	Red Dragon
0×10	Pyrolisk	Fire Hydra	Water Naga	Spirit Naga
0×14	Chimera	Rhyos	Mindflayer	Green Dragon
0×18	Blue Dragon	Clay Golem	Stone Golem	Iron Golem
0×1c	Death Knight	Dark Wizard	Dark Fighter	Nightmare
0×20	Death Machine	Manticore	Lich	Lich (Chaos)
0×24	Marilith	Marilith (Chaos)	Kraken	Kraken (Chaos)
0×28	Tiamat	Tiamat (Chaos)	CHAOS	Astos
0×2c	——	Echidna	Cerberus	Ahriman
0×30	Scarmiglione (cloaked)	Scarmiglione (undead)	Cagnazzo	Barbariccia
0×34	Rubicante	Gilgamesh	Omega	Shin Ryuu
0×38	Atomos	Typhon	Orthros	Phantom Train
0×3c	Death Gaze	Devil Wizard	Holy Dragon	Bloody Eye
0×40	Black Dragon	Earth Plant	Yamatano Orochi	Dark Elemental
0×44	Prototype

AI definitions

Table location: 0×22f17c — 0×22f5cb.

Data structure size: 16 bytes per AI entry.

Examples

Decoding AI information

Spell % and Ability %

These values I’ve misnamed a bit, as they are not technically “percent” values. IIRC, the game first checks to see whether the monster casts a spell. A random number is rolled between 1 and 0×80, or 128, and if this number is less than the value stated in Spell %, then the next spell in the individual monster’s queue is cast.

If the monster didn’t cast a spell, then the game checks whether it used an ability. This is done in the same manner, using another number rolled between 1 and 128.

Of course, if the monster didn’t cast a spell and didn’t use an ability, then it will attack. And a 00 in these values guarantees that the monster will fail its check to use a spell or use an ability (depending on where the 0×80 is placed).

Spell Queue and Ability Queue

Each AI is allotted a queue of up to eight spells, and up to four monster abilities. A monster may be able to cast spells, use abilities, and some intrepid critters can even do both of these things.

The first time a monster uses a spell, the game picks the first spell in the queue, and that’s the monster’s action. The second time a monster casts a spell, the second spell is used. When it reaches the end of the list (denoted by ff), the list gets reused. Setting the Spell (or Ability) % to a non-zero number, and setting the Spell (or Ability) Queue to all ff‘s will very likely lead to Very Bad Things. Don’t do this, it isn’t nice.

For help in figuring out what values correspond to which Spells or Monster attacks, you’ll need to refer back to the Spells and Monster Attacks article. The IDs listed there for the Spells is accurate. The IDs for Monster Abilities listed in that page do not correspond to the values in the AI table. To calculate what the IDs should be in the Ability Queue, take the ID from the Spells and Monster Attacks article and subtract 0×41.