dead said:
Is every demon published by WotC a ta'nari by default?
Likewise, is every devil published by WotC a baatezu by default?
In one Planescape product there's mention of "baatorians". Some ancient devil race or something. Not sure on the details.
Are ta'nari and baatezu what you'd call "races"?
Note: Alot of this info is from Planescape and may not officially apply in 3e, but I don't think I am contradicted anything published in 3e.
I don't believe they are defaulted to tanar'ri and baatezu. I think they default to "other" unless called out specifically. As someone who owns every single Planescape product, I can assure you, you have about as much information on the ancient Baatorians as I. They were there for flavor and possible adventure ideas.
The term Baatezu consists of a small, distinct set of creatures. They are indeed the same "race". A Pit Fiend was once a Lemure. He just "grew up". Interestingly, there is another Baatorian race - the Nupperibo - that can be mutated into a Baatezu. Most scholars actualy think it is a Baatezu because Baatezu can descend from them. In fact, it is rumored by some Baatezu (who are untrustworthy to say the least, but they're not 'Loths) that Nupperibo would naturally ascend to be that ancient Baatorian race referred to. That is why they are hunted down and used as fodder for the Blood War, or mutation stock.
I think 3e really messed alot of things up when it comes to outer planars. See, there are Baatezu who are all a specific race of devil. But what is a devil? A native to Baator? But the Barghest is native to Baator. What is the Barghest? Is it a devil? I would think so. But they're not listed under Devil in the SRD.
The term devil (I'll just talk about Devils as they are easier to categorize) is really just a label used by primes to categorize creatures that they know very little about (the Tanar'ri and Baatezu often find it insulting to be referred to as a Demon or Devil, especially vice versa). They are categorized by abilities rather than by idealistic, biological, or native link. Devils have telepathy. They are from Baator. They usually are resistant to acid and cold and immune to fire and poison. This is what defined Devil.
So anyway, you can use the terms as you want. If you are really interested in using "Baatezu" and "Tanar'ri" 3rd edition will not really help you. Sure, some of them are labeled as such, but they're just a bunch of stats. If you want to come up with your own ideas and motivations for Baatezu and Tanar'ri, then you don't really need to know if any individual creature is one of those because it's your game and you can change it how you will.
If instead, you want to use them as originally presented, I suggested you pick up a PDF copy of Faces of Evil: The Fiends. It's a pretty authoritative and definitive guide on Tanar'ri, Baatezu, and Yugoloths, with secondary attention paid to other Fiendish creatures (such as the Gehreleths). It is extraordinarily rules-light (maybe 5 pages total, discluding some charts in the back) and can be dropped into any 3e campaign. It's also thoroughly enjoyable to read, cover to cover. So if you don't use the info, you haven't wasted the money.
As an important note, I believe Wizards has added 3 new Devils (at least 2 new Abishai which should be entirely ignored in my opinion) and 2 new Yugoloths between their various monster supplements (I may be remembering incorrectly since Wizards muddled their fiendish monster line by publishing them across 4 separate books). You should be able to fit them in pretty easily with the information from 2e.