Ok. So, my friend is saying that the 3rd level ability for the Oni Bloodline, gives you the change shape ability and not the altered form ability, even though it says "as the spell altered form". He says they wouldn't have included change shape in the wording had they not intended you to be able to use that ability.
Altered Form (Sp): At 3rd level, you gain the ability to change shape (as the spell alter self) for a number of minutes per day equal to your sorcerer level. These rounds need not be consecutive. At 17th level, the duration of this effect is no longer limited, and you may remain in your chosen form as long as you want.
So, is there a faq or dev quote I can point him to, to end his silliness?
Looking at both the bloodline power and the monster ability....what is the difference in this case? Whether her gets alter self for minutes per day or he can use change form (which usually has a spell, such as alter self, as the basis for how it works in the description) for minutes per day does not appear to be that difference.
Wait....no there is a difference. Change form is worse.
This ability functions as a polymorph spell, the type of which is listed in the creature’s description, but the creature does not adjust its ability scores (although it gains any other abilities of the creature it mimics).
Ah, well then, not so bad. He was talking about changing into a hill giant and that seemed odd. Missed the part about not adjusting the ability scores.
Ok then, never mind. Nothing to see here.
wait, a hill giant? No, that is not how this change form works, or any unless it is specified as such.
You are correct in telling him he can't do this because the ability specifies alter self. The rules state that change form works like the spell it lists (minus adjustments). The ability given at level 3 only does medium and small creatures.
Admittedly there is an ability, the level 20 capstone, that lets him use Giant form I (at will and as long as he wants, but his choice in giant subtype is locked in). That does not specify change form, so he might get the adjustments, but hey, he would be a level 20 sorcerer. Giant form I is the least of what he can do. He could have had that spell since level 14 anyway.