Quote Originally Posted by Eldan View Post
We can basically go by player class archetypes:

Brute: d10 HD, High base attack, high fort, 2+ skill points
Trickster: d8 HD, medium base attack, high reflex, 8+ skill points
Specialist: d6 HD, low base attack, high will, 6+ skill points
Allrounder: d8 HD, medium base attack, one high save (varies), 4+ skill points
Paragon: d10 HD, high base attack, all high saves, 8+ skill points. For those outsiders and others like them who are just good at everything.

These honestly already cover just about all the monsters out there.

I don't think AC and mobility need to be tied directly to this and neither do special abilities. Hit dice should only determine HD-dependent numeric values.
Quote Originally Posted by Durzan View Post
Monsters already treat whatever skills that are listed in their entry as class skills, so that part is kind of redundant in nature. The only reason you'd want to give them additional class skills on top of that would be if you want that specific monster to have special training in additional areas... which is rare and can typically limited to monsters who can gain class levels anyway.
My mention of class skills and special abilities was regarding using monster classes as classes, not just a kind of HD; that is, each class grants special attacks and special qualities at certain levels off a class-based list, so you'd want more than five classes for that, probably 8ish would be good but I could see going up to 10 or 12. That would make monsters a bit more normalized in their miscellaneous abilities and natural armor, DR, wouldn't just be pulled out of the designers'...portable hole. So the "Brute" class gives you certain HD and bonus progressions and also lets you pick up high natural armor and DR, Harrier gives you certain HD and bonus progressions and also lets you pick up speed boosts and extra attacks, and so on. And certain slots would be for type- and subtype-related features regardless of class, like SLAs for Outsiders, gaining or increasing fly speeds for (Air) creatures, and so on.

That way, a vrock (for instance) gets certain abilities automatically because it's a vrock, then can choose certain abilities because it's an Outsider/Spirit/Immortal/whatever, certain abilities because it's a (Chaotic, Demon, Evil) creature, and certain abilities because it's a Harrier, basically treating "vrock" as a race and "Outsider Harrier" as a class, as Durzan suggested. This has a couple benefits: advancing a monster (or de-leveling it to represent a weaker/younger version) has defined effects instead of just ""; there are good benchmarks for what a creature of a given type, class, and HD should have as far as number and magnitude of special abilities; if a player wants to play a dragon or angel or something you can just straight-up say "We'll decide on N racial traits and then you can build your monster however you want by the normal monster class rules;" transformative classes like Dragon Disciple, Fiend-Blooded, and the like can let you take traits from appropriate monster lists instead of hard-coding a few boring stat boosts to represent being a dragon/fiend/etc.

If you only want classes to grant featureless HD, obviously none of that's necessary and 4-5 classes is probably sufficient just like 4-5 types' worth of racial HD is sufficient.

Spirits in my campaign settings are personifications of specific aspects of nature (kind of like what we see in Avatar the Last Airbender) and are tied specifically to the material plane. They govern and influence the part of nature they personify, and as a result have specific traits unique to them (that I've added) that make them distinct and unique from outsiders. Spirits are immortal (meaning, they cannot die of old age): if you kill their physical body, the soul of the spirit leaves the body and assumes an incorporeal form. Then the spirit tries to return to the place where it originated from on the material plane. If it does so, it regains its physical body over the course of a 24 hour period. However, if you manage to reduce the spirit's incorporeal form to 0 HP, then it is permanently destroyed.

Meanwhile... outsiders are powerful, other-worldly beings entirely. Some originate from other universes, others are formed from the souls of long-dead individuals, still others are etc. Outsiders do not necessarily have a dual nature (while Spirits specifically do in my setting), and may be alien in appearance and thought process. They may or may not be Immortal. The most powerful Outsiders could rival the gods of my setting in power... indeed, the 3 Demon Lords (The term Demon being repurposed to mean any evil outsider within the confines of this campaign setting) are effectively the setting's "Evil Dieties," although they are not technically dieties. Thus, thematically they shouldn't be considered spirits.
Outsiders are also strongly tied to their plane of origin, so you could make them both one type and just have the (Spirit) subtype grant the turn-incorporeal-and-flee property, similar to how Outsider (Native) creatures have different rules for banishment and resurrection than normal Outsiders in the core rules.