SRD said:
Disguise Self
Illusion (Glamer)
Level: Brd 1, Sor/Wiz 1, Trickery 1
Components: V, S
Casting Time: 1 standard action
Range: Personal
Target: You
Duration: 10 min./level (D)
You make yourself—including clothing, armor, weapons, and equipment—look different. You can seem 1 foot shorter or taller, thin, fat, or in between. You cannot change your body type. Otherwise, the extent of the apparent change is up to you. You could add or obscure a minor feature or look like an entirely different person.
The spell does not provide the abilities or mannerisms of the chosen form, nor does it alter the perceived tactile (touch) or audible (sound) properties of you or your equipment.
If you use this spell to create a disguise, you get a +10 bonus on the Disguise check.
A creature that interacts with the glamer gets a Will save to recognize it as an illusion.
I'm not sure if a face is a "minor feature". That seems like a stretch.
Alter Self lets you change into a creature of the same type (such as Humanoid). It specifically says "You do not gain any extraordinary special attacks or special qualities not noted above under physical qualities, such as darkvision, low-light vision, blindsense, blindsight, fast healing, regeneration, scent, and so forth." So unless there's a Humanoid creature (most PCs are Humanoids) with no internal organs, or is otherwise naturally immune to critical hits (as opposed to being immune through some extraordinary ability), then
Alter Self won't do the job.
Polymorph lets you turn into any monster that's within your hit dice range, though "any" is limited: It can be "aberration, animal, dragon, fey, giant, humanoid, magical beast, monstrous humanoid, ooze, plant, or vermin."
Now, is thee such a thing as a Troll with an eye on his nose and a third arm? Maybe. Consult with your DM to be sure.
Note that even if the answer is "Yes", your three armed, one eyed Troll won't have Regen'. You gain extraordinary special attacks of the new form, but not extraordinary special abilities or supernatural abilities of the new form.
So transforming into a Dragon would give you size, wings and a breath weapon, but no fear aura or spell like abilities. (I might be wrong about the breath weapon.)
If your goal is to become immune to critical hits,
Polymorph into an ooze or plant.
Transforming into an Elf with no internal organs still doesn't work though, since there is no such creature. You are, after all, limited to creatures that actually exist in your game world.
