How is Polymorph “broken”?

Question

I have read numerous posts from various websites saying that the wizard/sorceror spell "polymorph" breaks game balance. Even Wizards of the Coast somewhat admits that. Sticking to just the core games rules, how does this spell swing game balance totally askew? Perhaps I am just not creative enough to understand the extent to which the spell can make normally challenging situations trivial. Please give examples, broken down at various ranges of character levels (from 7th level, when a wizard first gains access to polymorph, up to 20th level)?

Update (12/18/2012):

There are some great answers here. I should have posted originally about the entire polymorph chain of spells instead of just the spell "polymorph" itself, but I think most of the answers so far took the question to mean the polymorph chain.

I do want to clarify slightly what I meant in my original question about examples, in the hopes of finding more of the "loopholes" that some have mentioned. The answer about the Avariel is a good one (gaining Fly at a longer duration at CL3 than at CL5 with the Fly spell). Any more examples of overpowered usages of the polymorph spell chain are welcome.

Answer 1

The main issues with Polymorph are:

• Monsters aren't designed for PC use. Many monsters have abilities that are overpowered or disruptive in the hands of PCs, as they were designed primarily as opponents and weren't balanced with polymorph in mind.

• Versatility is power. Polymorph is by far one of the most versatile spells in the book. A more versatile character is actually more powerful, since he's more likely to have the most effective solution to any given problem. Polymorph gets more versatile for free as you add new monster books.

• Polymorph isn't as broken as it used to be, but there are still loopholes. Because not all monsters were written with polymorph in mind, polymorph has numerous, very specific limitations. However, some forms have powerful or disruptive abilities which aren't covered by these limits.

Some particular uses for polymorph:

• Annis hag (7 HD): Large size with 10 ft. reach, +10 natural armor, Str 25, and can still use weapons, cast spells and wear humanoid magic items. Two claws, bite, rend, improved grab and rake.
• Mind flayer (8 HD): Four tentacle attacks and Extract (Ex). A good grapple can instantly kill any opponent. Alternatively, a rogue can use all four tentacles to make sneak attacks.
• Dark naga (9 HD): Poison sting, DC16 or fall asleep for 2d4 minutes. Sleeping opponents can be hit with a coup de grace.
• Roper (10 HD): Large size, 14 natural armor, 19 Strength, 50 ft. reach with ranged touch attack that inflicts 2d8 points Strength damage (Fort 18 negates). A full attack allows six strands, plus a bite with 10ft. reach and 2d6 damage.
• Guardian naga (11 HD): Poison (bite, or ranged touch spit), DC 19 and initial and secondary damage 1d10 Con. 7 natural armor, Str 21 and Con 19, too.
• Cornugon (15HD, requires Outsider type from planetouched race or Otherworldly feat): Large size with 10 ft. reach, 19 natural armor, flight, 31 Str, 25 Dex, 25 Con. Can still use weapons and wear equipment.

There are a few ways to curb the excesses of polymorph without banning it outright.

1. Limit the players to assuming forms of creatures they've actually encountered. This prevents cherry-picking the most broken options from monster books.
2. Don't allow armor to resize when the character assumes Large size. The rules don't strictly say that armor resizes (although it does suggest that "Size should not keep characters of various kinds from using magic items"). This prevents Large forms with high natural armor from being too powerful.
3. Pay close attention to which forms the polymorph rules actually allow. For example, you cannot assume the form of a templated creature, or a creature of a size more than one larger or smaller than your own.
4. Take a look at Pathfinder's version of polymorph.

Answer 2

Wizards of the Coast explain this problem here. The ways this spell is used and abused are summarized here.

As some examples of this whole subschool being broken:

1. Alter Self into Avariel - you just got yourself a cheaper and longer version of Fly two levels early
2. Start as an outsider and Alter Self into Ravid - you just got yourself +15 of Natural Armor (not that it's much, but really, should a second level spell produce that sort of effect at CL3?)
3. Or just go Polymorph your party rogue into a Hydra - lots of attacks and full attack at every opportunity (Opportunist anyone?)

The problem, of course, is that we are just getting started...

The core gives much less options for polymorphing into, so could be considered more-or-less safe, at least in the part that caster's options about this spell are not unlimited. And the Pathfinder version of this subschool could be considered fixed - it explicitly states what you can get from each spell.

Answer 3

The word "broken" has different meanings to different people. Polymorph fits a few of those, which is why we have a lot of people saying it about the spell.

In core 3.5, the fundamental problem is that the spell's power is not bounded by the contents of the spell description, it is bounded by the power of the monsters available. This has a few consequences:

• The spell is more versatile than any other spell of its level, capable of being useful in almost any kind of encounter.
• It so happens that there exist monsters with raw numbers much more powerful than those expected of equivalent-level PCs.
• It grants access to special attacks not normally accessible to PCs.

Out of core, the list of problems gets bigger as the list of monsters (and supporting material) gets bigger. Particularly, feats such as Assume Supernatural Ability [Savage Species] and Metamorphic Transfer [Expanded Psionics Handbook] add a whole new dimension to what Polymorph and its relatives can do.

Eugene's post contained an excellent link to listings of the more useful Polymorph forms, broken down by level ranges as you requested. You asked for forms up to level 20, but (in core) the spell caps out at level 15 as far as new forms are concerned. Thus, the core monster lists end there.

Answer 4

Another broken aspect is that it messes up point-buy for ability scores. You can choose to dump your physical stats when you make your character, focusing entirely on mental stats, and then use polymorph to give yourself great physical stats as well.

And that's just one spell to do it; you still have plenty more.

Answer 5

I’m only answering the update section, since the problems with polymorph have been well-addressed.

Polymorph any object is like polymorph but much better. It potentially lasts much longer (and, in fact, RAW two castings simultaneously cause it to become Permanent), and a lot of the restrictions in terms of type and HD are removed.

But shapechange is just absurd. The lack of Supernatural abilities on the earlier forms was the only significant limitation on them (well, that and HD caps, but shapechange still has those, though they are higher). The Supernatural abilities of monsters are ridiculous. Consider the Choker’s Quickness (Su) – two Standard Actions per turn. That’s immensely powerful, and the caster of shapechange can get it trivially. And you can change form as a Free Action, bouncing around between shapes as you please, over the course of the spell’s long duration.