I want to give full credit to Quadratic Wizard’ answer for finding the relevant rules text here, because I wasn’t aware of it (and frankly didn’t believe it existed), but I have to offer a competing analysis of the text.
Bottom Line Up Front:
With the addition of the statements made in the “Lack of Intelligence” section on page 23 of Savage Species, the question solely comes down to whether or not Savage Species is allowed to establish “core-ish” rules. If yes, then we have an answer (“permanent” increases to Intelligence to 3 or greater turn an animal into a magical beast, temporary increases cannot increase its Intelligence above 2 at all). If no, then we don’t have an answer and I strongly doubt we’d ever be able to establish one (but then again, I was surprised to learn of this section in the first place, so perhaps I’ll be surprised again).
If you really must have “the correct, rules-as-written interpretation” here, unfortunately, it’s “no” to Savage Species, and thus “undefined” to the overall question.
First, the text, with a little more context:
Lack of Intelligence: Players who want to play some kind of construct, undead, animal, or plant face this obstacle. […] A creature may also circumvent its lack of Intelligence with a magic item that boosts Intelligence, such as a headband of intellect. Items that raise Intelligence temporarily (such as a potion of Intelligence) do not remove this obstacle.
When the Intelligence of an animal permanently rises above 3, the creature becomes a magical beast.
(Savage Species, pg. 23)
The opening of this section is, I feel, absolutely critical to understanding the rule here, since without it we have a sentence referring to “this obstacle” without being entirely clear what obstacle we’re referring to—some kind of lack of Intelligence, sure, but how far does it go? The full context makes it clear that it goes all the way—Savage Species not only allows a headband of intellect to increase an animal’s Intelligence above 2, but it even allows one to make a mindless creature intelligent!
It is, I think, very clear now that Savage Species is definitely adding new “core” rules here—because under the actual core rules, a headband of intellect couldn’t do that. Mindlessness means having Intelligence as a “nonability,” that is, “These creatures do not have an ability score of 0—they lack the ability altogether,” (Nonability definition, also found in the core Monster Manual). With nothing to add a bonus to, the bonus doesn’t apply—this is explicitly not 0+X, it’s
undefined+X (my browser console tells me that equals
At this point, I no longer really care about the core definition of a “permanent” bonus or a “temporary” bonus, versus the Savage Species definition. It’s very clear that Savage Species is writing its own new rule here, and the fact that it’s re-using terminology is the least of our concerns. (The fact that the game goes very far out of its way to avoid making the distinction between a permanent and a temporary bonus almost ever matter is a big part of this, too—it’s really easy to not even know about that core rule ’cuz it affects so few things.)
The bigger question is whether or not Savage Species gets to do this. To answer that, you first have to answer whether Rules Compendium gets to do it. To make matters worse, though, Rules Compendium at least explicitly asserts that it is doing that and is supposed to do it: “[The book] updates […] the rules, as well as expanding on them,” (Rules Compendium, pg. 5). Savage Species makes the opposite claim: “this book features several changes to the rules concerning monsters. The changes […] are also reflected in the D&D game’s revised core rulebooks, particularly the revised Monster Manual,” (Savage Species, pg. 4). According to Savage Species, anything you find in that book should be consistent with what winds up in the “revised core rulebooks,” since it was published before the “v.3.5 revised edition” was. And predictably... it didn’t actually turn out that way all of the time.
Ultimately, there are no answers here. Is this a Savage Species-specific rule? A rule that Savage Species thought was going to become core, but never did? A rule that was going to be core, but then was specifically edited out? A straight-up mistake? We’ll never know. By the errata rules, Savage Species doesn’t get to make this rule—the primary source on ability scores, nonabilities, magic items, bonuses, and so on, are the core books, not Savage Species, and Savage Species doesn’t even give us its own assertion of primacy to work with as Rules Compendium does. And this rule is clearly in contradiction with core, at least with respect to mindless creatures. So I guess, RAW, it’s out.
But that leaves us with no answer at all, because absent this claim from Savage Species, the entire situation is unresolvably ambiguous.
- Because I know HeyICanChan, at least, will wonder—I do make a distinction here between adding a bonus to a nonability, versus stacking levels, with one’s levels in a class one hasn’t taken. The distinction is akin to that between a numerical sum and a set union. Which is questionable in the extreme, but if push comes to shove, I’m much more likely to give way on the level stacking thing than I am on this nonability plus a bonus thing, so none of that concern is specifically relevant to this question.