What are the repercussions for continuous usage of polymorph spells?

Question

There are several items that allow for continuous duration alter self such as the FleshShifter Armor (Book of Vile Darkness) and the Skin of Proteus (SRD). Using these allows a character to act as a member of a different race without actually having to pay the costs for playing that race. Are there any rules as to the long-term effects of this kind of behavior on skill points and experience game?

For example if an Sun Elf with a racial bonus to intelligence uses one of these items to act as a dwarf 24/7, they do not get to use the racial bonus to intelligence and instead can make use of a racial bonus to Constitution, which gives them extra hit points all the time. However, when they level up do they still use their actual intelligence bonus to determine additional skill points, or is there some sort of penalty for staying too long in a form that deprived them of that intelligence bonus?

Likewise a human with the feral template counts as a monstrous humanoid and could therefore use one of these items to take the form of a Thri-Kreen, which has four clawed arms, two racial hit dice, a bonus feat, natural armor, and some handy psionic abilities. If this character stays in that form all of the time is there any penalty to the experience points they accrue due to having been in a form with two racial hit dice and two points of level adjustment?

Answer 1

None of this is defined at all

There’s just no rule for any of these things.¹

Whether temporary effects apply during level-up

Using temporary bonuses while leveling up is a theoretical-optimization mainstay, but that’s taking things from an extremely generous “all plausible rulings in our favor” point of view.

There is some basis for this. Very, very few things in the game care “how” you have the statistics that you do. There’s a few key things where the game tracks “base” stats—base attack bonus, base save bonus, and skill ranks—but those are the exceptions that prove the rule. We don’t have “base” Intelligence or “base” abilities—we just have whatever we have, however they got there. Or, at least, the rules lack any terminology for referring to such things.² That implies that any such distinctions are arbitrary, not a part of the rules.

But, of course, the DM is explicitly there as an arbitrator. It’s their job to make such distinctions in corner cases that the rules haven’t covered. The books make no claim to cover every eventuality. And it’s a real stretch to say that the lack-of-rule here is actually an endorsement.

Whether RHD or LA from temporary forms affects when you level-up

This has even less information on it. Alter self says

You acquire the physical qualities of the new form while retaining your own mind. Physical qualities include natural size, mundane movement capabilities […], natural armor bonus, natural weapons […], racial skill bonuses, racial bonus feats, and any gross physical qualities […].

Is LA any of these things? Probably not, but it’s hard to say for sure. What about RHD? Those are... more physical, but are they the same as these?

Likewise, about things you don’t get, we have

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.

You do not gain any supernatural special attacks, special qualities, or spell-like abilities of the new form. Your creature type and subtype (if any) remain the same regardless of your new form. You cannot take the form of any creature with a template, even if that template doesn’t change the creature type or subtype.

Now does any of this cover LA or RHD? It’d be real, real hard to claim they’re extraordinary abilities. They certainly aren’t listed under special attacks or special qualities in monsters’ statblocks. They are their own thing—which is not mentioned under things you do gain or under things you don’t gain. I suppose we should default to you not getting them, except...

You assume the form of a creature of the same type as your normal form. The new form must be within one size category of your normal size. The maximum HD of an assumed form is equal to your caster level, to a maximum of 5 HD at 5th level.

This kinda makes it sound like you do get the RHD, at least, as part of the “form.” Though of course it’s entirely possible that this is being used purely as a gate-keeping device on when you can assume certain forms and is unrelated to what actually happens when you do. LA is still AWOL.

And then even if you get them, do they count? Your guess is as good as mine. Again, optimizers tend to assume “No,” and there is some basis for it: NPCs don’t have their abilities count against them in this manner, so why should PCs?

Do not award XP for creatures that enemies summon or otherwise add to their forces with magic powers. An enemy’s ability to summon or add these creatures is part of the enemy’s CR already. (You don’t give PCs more XP if a drow cleric casts unholy blight on them, so don’t give them more XP if she casts summon monster IV instead.)

^{(Dungeon Master’s Guide pg. 37)}

This addresses summoning, but shapechanging is the same kind of idea. In theory, the ability to take on that form is balanced by various factors and appropriate to the PC’s actual level, so using those abilities shouldn’t make them earn less XP. That’s a wonderful theory, but well, we know the game isn’t remotely balanced.

Still, personally anyway, I despise anything that makes me calculate separate XP awards for individual PCs. I eliminate all of them from my games, and recommend everyone else do the same. No split levels, no XP costs, no LA, nada. Everyone stays at the exact same HD, ECL, and XP value. This is obviously not where the rules are, but in this one regard—that shapechanging magic shouldn’t be altering ECL on the fly—I’ll accept their lack-of-rule as being in the right place.

1. _{Well, technically, there is one rule relevant to the points you raised in the question: alter self explicitly states that “A body with extra limbs does not allow you to make more attacks (or more advantageous two-weapon attacks) than normal,” so using it to become a thri-kreen doesn’t offer the “four clawed arms” you mention in the question. That’s rather tangential though.}

2. _{Perhaps tellingly, Paizo’s Pathfinder spin-off went out of its way to define “temporary” and “permanent” bonuses to things, to try to clarify some of this. That they felt the need to do that suggests that in 3.5e, there wasn’t any such distinction. But they could have had other reasons for doing so.}

Answer 2

Concerning the first part of your question: The Player’s Handbook distinguishes between permanent and temporary changes to a character’s intelligence score:

Your character’s Intelligence modifier affects the number of skill points he or she gets at each level (see Table 1–1: Ability Modifiers and Bonus Spells, page 8). This rule represents an intelligent character’s ability to learn faster over time. Use your character’s current Intelligence score, including all permanent changes (such as inherent bonuses, ability drains, or an Intelligence increase gained at step 4, above) but not any temporary changes (such as ability damage, or enhancement bonuses gained from spells or magic items, such as a headband of intellect), to determine the number of skill points you gain.

PHB, 58

Magic items that have continuous effects – like the ones you mention - can theoretically be active indefinitely. Still, their effects are not permanent, because you are free to take them off any time (like the Headband of Intellect given as an example in the text). They only provide temporary changes.

So, if the Flesh Shifter Armor or the Skin of Proteus gave a character a new INT score, it would not influence the number of skill points they get while levelling up. — But, actually, these items leave the INT score unchanged anyway, because (as michael points out in his answer) Alter Self, Polymorph or Metamorphosis let you keep your own INT, WIS and CHA scores (which includes any racial ability modifiers).

I would likewise rule that racial HD and Level Adjustment of a form you temporarily aquire do not affect the way you gain experience points.

Answer 3

TL;DR:

• Your elf would not lose their racial intelligence bonus; their Int score would remain unchanged.
• Transforming into a dwarf using Fleshfiter Armor would not change the character's Con bonus or hit points.
• Transforming into a dwarf using a Skin of Proteus would grant the default physical ability scores of the base creature (Str 10 Dex 10, Con 12).¹ Their HP would be updated according to their new Con bonus using the character's own HD, not the target creature's.
• Transforming into a Thri-kreen would ...
  • grant the racial bonus feat Deflect Arrows, but not the feat Thri-kreen's gain from their starting HD (ie: you don't get multi-attack).
  • grant its nat armor bonus.
  • not grant 2 bonus HD; with either effect the characters HD remain unchanged.
  • not grant its psionic abilities.
  • not modify your character's ECL (no level adjustment).

Explanation follows.....

Let's start by looking at the abilities you mentioned as examples and the effects they emulate: Fleshshifter Armor emulates alter self and Skin of Proteus emulates metamorphosis. Both spells limit you to creatures with no more than 1 HD / caster level (minimum of 3 for Fleshshifter Armor and 7 for Skin of Proteus). If the items were crafted at a higher caster level, alter self allows forms up to 5 HD at CL5, and metamorphosis up to 15 HD at CL15 (provided you pay the increased cost for crafting the item at a higher caster level).

How both effects are the same:

• You retain all supernatural and spell-like special attacks and qualities of your normal form, except for those requiring a body part that the new form does not have (such as a mouth for a breath weapon or eyes for a gaze attack).
• You keep all extraordinary special attacks and qualities derived from class levels, but you lose any from your normal form that are not derived from class levels.
• If the assumed form is capable of speech, you can communicate normally.
• You can cast spells or manifest psionics, provided your new form is able to speak intelligibly (that is, speak a language) to use verbal components and must have limbs capable of fine manipulation to use somatic or material components.
• You retain your own mind; your Int, Wis, and Cha are unchanged.
• You obtain the target form's natural size, mundane movement capabilities (such as burrowing, climbing, walking, swimming, and flight with wings, to a maximum speed of 120 feet for flying or 60 feet for nonflying movement), natural armor bonus, natural weapons (such as claws, bite, and so on), racial skill bonuses, racial bonus feats, and any gross physical qualities (presence or absence of wings, number of extremities, and so forth).
• You do not gain the target form's extraordinary, supernatural, or spell-like abilities; you do not gain any physical qualities not listed above (eg: darkvision).
• You can freely determine the minor esthetic qualities of your new form (eg: hair color, etc.).

Metamorphosis is different from alter self in several ways:

Ability scores:

• Alter self: You retain your own ability scores.
• Metamorphosis: You gain the Strength, Dexterity, and Constitution scores of the new form but retain your own Intelligence, Wisdom, and Charisma scores.

Creature type:

• Alter self: Your type is unchanged; you cannot assume the form of a different type.
• Metamorphosis: Your type and subtype change to match that of the new form, which can be any type except any other type except construct, elemental, outsider, and undead; nor can the form be incorporeal, ectoplasmic, or gaseous.

Size:

• Alter self: Within one size category of your normal form.
• Metamorphosis: No form smaller than fine (or so large it exceeds the HD limit).

Metamorphosis provides some HP regeneration when you change forms. It also allows the character to transform into inanimate objects, but that does not really apply to your question.

In other words, how a character levels would unaffected by using either effect indefinitely -- intelligence is unchanged (and therefore so are skill points), HD is unchanged, and the qualities one does gain from the new form do not really warrant taking on the target creature's level adjustment.

Hope this helps!

¹ or with a more generous DM, the physical stats from the Dwarf War1 entry in the Monster Manual: Str 13, Dex 11, Con 14 (https://www.d20srd.org/srd/monsters/dwarf.htm)