In the description for Primal Transformation, it says
"While transformed in this way, the animal companion's type changes to magical beast, though the primal companion hunter still treats it as an animal for the purpose of the Handle Animal skill."
Now, when it says the type changes, what exactly does that change? Is it just a cosmetic change? Or do they gain the following things effective immediately, and then revert to their normal stats once the Transformation wears off?
Magical Beasts have:
d10 Hit Die.
Base attack bonus equal to total Hit Dice (fast progression).
Good Fortitude and Reflex saves.
Skill points equal to 2 + Int modifier (minimum 1) per Hit Die. The following are class skills for magical beasts: Acrobatics, Climb, Fly, Perception, Stealth, Swim.
Darkvision 60 feet.
Low-light vision.
Proficient with its natural weapons only.
Proficient with no armor.
Magical beasts breathe, eat, and sleep.
Animal companions use a druid's BAB equal to their hit dice for attack. Skill points, class skills, proficiency, and the necessity to breathe/eat/sleep are not changed because magical beasts are general rules compared to the specific ones found in each animal companion's stat block. If any of the animal companions had a statement of "animal qualities," then I could see it being valid to switch it to magical beast qualities for where there are differences.
Essentially, the only thing that does change is that spells affect the companion as if it were a magical beast instead of whatever its previous form was (which is most likely an animal). If a spell calls out for an animal target, then the companion can no longer be targeted by that spell while Primal Transformation is in effect. The only exception is for the purposes of the Handle Animal skill.
The only possible opening is to hit points, which I doubt would be changed for many reasons.
Ok, I was just confused because it said that they became a magical creature...and honestly D10 and full BAB would have been absolutely incredible.
It makes sense that it only applies to what spells effect them otherwise they would be absurd, but I wish that was written more clearly since the rules just say "Now they are a magical beast," and I had to figure out what they meant by that.
Though it would have been really awesome if it did give them full BAB >_>