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The Polymorph Problem aka: Brontosaurus-Ant

Feast your eyes:

Polymorph Other (Alteration) Level: 4 Range: ½"/level Duration: Permanent

Saving Throw: Neg. Area of Effect: One creature

Components: V, S, M Casting Time: 4 segments

Explanation/Description: The polymorph other spell is a powerful magic which completely alters the form and ability, and possibly the personality and mentality, of the recipient. Of course, creatures with a lower intelligence cannot be polymorphed into something with a higher intelligence, but the reverse is possible. The creature polymorphed must make a "system shock" (cf. CONSTITUTION) roll to see if it survives the change. If it is successful, it then acquires all of the form and abilities of the creature it has been polymorphed into. There is a base 100% chance that this change will also change its personality and mentality into that of the creature whose form it now possesses. For each 1 point of intelligence of the creature polymorphed, subtract 5% from the base chance.

Additionally, for every hit die of difference between the original form and the form it is changed into by the spell, the polymorphed creature must adjust the base chance percentage by +/-5% per hit die below or above its own number (or level in the case of characters). The chance for assumption of the personality and mentality of the new form must be checked daily until the change takes place. (Note that all creatures generally prefer their own form and will not willingly stand the risk of being subjected to this spell!) If a one hit die orc of 8 intelligence is polymorphed into a white dragon with 6 hit dice, for example, it is 85% (100% - [5% X 8 intelligence] + [(6 - 1) X 5%] = 85%) likely to actually become one in all respects, but in any case it will have the dragon's physical and mental capabilities; and if it does not assume the personality and mentality of a white dragon, it will know what it formerly knew as well.

Another example: an 8th level fighter successfully polymorphed into a blue dragon would know combat with weapons and be able to employ them with prehensile dragon forepaws if the fighter did not take on dragon personality and mentality. However, the new form of the polymorphed creature may be stronger than it looks, i.e. a mummy changed to a puppy dog would be very tough, or a brontosaurus changed to an ant would be impossible to squash merely from being stepped on by a small creature or even a man-sized one. The magic-user must use a dispel magic spell to change the polymorphed creature back to its original form, and this too requires a "system shock" saving throw. The material component of this spell is a caterpillar cocoon.


You wanna know what, and I’m gonna to tell ya. You learn not to ask the internet how to handle things like this. It’s often just better you figure it out on your own, which makes this post hypocritical in an inextricable yet humorous way. Flee. Abscond. Be happy in the way you’ve managed this spell for your own campaign.

No, Anthony, I want you to tell me things.

Okay. Let’s say you want to run your game RAW, but then you hit a spell like this during play and realize (possibly for the first time) that AD&D is booby trapped. I address another of these "booby traps" over here with regards to the Ring of Spell Turning.

Consider the questions I ask myself after reading the Polymorph Other spell:

“So uh…isn’t a blue dragon almost always smarter than a fighter? So then, doesn’t that contradict the part where it says creatures with a lower intelligence cannot be polymorphed into something with a higher intelligence? Also that math is uh...well, what does the formula imply?


100% - [Target’s INT x5] + [New Form’s HD – Original Form’s HD x5].

Bug to human:

(100% - [0 x 5]) + ([1 - ⅛] x 5) = 104% of gaining a human personality.

Human to bug:

(100% - [10 x 5]) + ([⅛ - 1] x 5) = 46% of gaining a bug personality.

Human to dragon:

(100% - [10 x 5]) + ([11 - 1] x 5) = 100% of gaining a dragon personality.

Dragon to human:

(100% - [17 x 5]) + ([1 - 11] x 5) = 65% of gaining a human personality.

Pet Dog to Bulette:

(100% - [1 x 5]) + ([9 - 2] x 5) = 130% of "Backpack" acting like a ravening Bulette.

Friendly Sage to Bulette:

(100% - [18 x 5]) + ([9 - 1] x 5) = 50% of the sage trying to bite your head off.

Friendly Sage to Nilbog:

(100% - [18 x 5]) + ([1 - 1] x 5) = 10% of the sage going crazy on you, as nilbogs do.

I guess if you've got a low INT and [or] are trying to become more powerful than you have a right to, odds are good you'll lose your mind. But hey, what does "mentality" mean?

The dated definition (Which Gygax may very well have intended) means the "capacity for intelligent thought". But I think it more likely he meant "characteristic attitude or way of thinking." What does it mean that a mummy changed into a puppy dog would be very tough? Or that a brontosaurus changed into an ant would be impossible to squash for a man-sized creature? The DIFFERENCE in HD between the original form and the new form are called out as part of the formula in determining if personality changes.

But it seems like this is simply part of the formula and that the new form does NOT get to re-roll hp based on the new HD.

See DMG p.45, which points out additional caveats: "Level of experience is not a part of a character's form, so it is quite foolish and totally impossible to attempt to polymorph a creature into an nth level character. Likewise, profession is not form, so attempting to polymorph to a fighter, thief, etc. results in human form and nothing more. Shape changers (lycanthropes, deities, druids, al.) will be affected for but one round, then will return to their former form.

Interesting. To me, this indicates that Gygax rarely had clean definitions for what mechanics actually represented fictionally in the game world. His explanation of HP (DMG p.82) showcases this. What the mechanic represents fictionally is often malleable, which serves the narrative of your adventure quite well. That's a whole other discussion.

In any case, it seems obvious that when a target is polymorphed it keeps whatever hp it had prior to the transformation (eg. brontosaurus-ant)

If you change an ant into a brontosaurus, then, it stands to reason that the transformation borders on illusion magic, for the dinosaur will likely die if you bat it with a rolled up pamphlet.

Let's also keep in mind that this is a fourth level spell, meant to open the door for creativity, which is wonderful. But unless the DM is vigilant, it also opens the door for degeneracy. Essentially, when you can do anything, there's often just ONE thing to logically choose: the antithesis of creativity.

Also, 4th level is powerful, but compare this spell with Shape Change, which is one of the highest level spells a magic-user can cast. Now you begin to suspect that what you want Polymorph Other to be if you're a Player and what you hope Polymorph Other is not if you're a DM are not only the same thing, but that the DM is standing on firmer ground.

With Shape Change, the caster BECOMES the creature and has ALL abilities save those dependent upon Intelligence (Example: becoming a very smart sort of creature would not necessarily bestow the ability to see through illusions for example [see Deities and Demigods p.7])

But ALL other abilities, presumably breath weapons, teleport without error, paralyzation and so forth WOULD be part of the deal. That's 9th level magic, for sure.

Polymorph SELF explicitly states that magical abilities of the new form are NOT part of the deal, nor are attack routines. But Polymorph OTHER states that the creature gets the form and ALL abilities of the new creature. But wait, further below the spells states that the target in the example is "85% likely to become a dragon IN ALL RESPECTS, but" (even if it doesn't) "it will have the dragon's physical and mental capabilities."

Compare this again with the DMG p.45 stating explicitly that the ONLY powers or abilities bestowed are related to FORM. Hmmmm.

From the very beginning of this post I told you to go and do as you wish with this spell, right? But since you are still here, I will tell you how I've come to handle it in our campaign and I'll start out with an example that happened in one of our most recent games.


The party is high in the mountains, on their way to Geir Loe Cyn-crul, when they are set upon by six Ettins. Awh'Gnuyk (an NPC succubus in the party [very long story]) Suggests one of the Ettins into a long-term cooperative relationship. He then helps slay the other Ettins.

The party, having raised a Green Dragon from egg to Adult, has finally been able to hail said dragon and secure flight for a portion of the 10-character party. They are tired of traveling on foot (which has occupied 4 game sessions). But with a party so large they need additional means of flight. The bard-in-training volunteers to be polymorphed into a red dragon for this purpose, but the cunning Green Dragon dissuades him by inquiring why they would not simply polymorph the Ettin and thereby avoid risk.

Convinced, the Magic-User casts Polymorph Other on the Ettin. I assume a CON of 18, which allows a 1% chance of death. This does not transpire. We then check the math and make the roll for the "mentality".

The Ettin fails? Is that the right word? And assumes the personality of a Red Dragon. I rule that because personality changed, the succubus' suggestion is also instantly cancelled. Fortunately, the Lyan (lawful-neutral paladin) has the Tamaraith's Whip from the Mortuary Temple of Esma. He whips the dragon, thereby issuing a Demand, that it submit to the magic of the wizard (who is casting Charm Monster). The Ettin attacks with its claws and breathes...but no breath weapon emerges. My ruling is that dragon breath is a magical ability, unrelated to form and, although the Ettin is now behaving like a Red Dragon, its abilities are limited. As such, it possesses no Fear Aura either. The dragon's claws, however, are just as dangerous as a real dragon's claws. Fortunately, they miss. Finally the Charm Monster spell resolves, no save is allowed (per the Demand) and control over the Ettin-Dragon is re-established.

It is past time that I reveal how I would re-write Polymorph Other, not to change it, but to:

  • Clarify its capabilities and risks

  • Ensure that Players and DMs alike understand that its power is well below that of Shape Change

Polymorph Other (Alteration)

Level: 4

Range: ½"/level

Duration: Permanent

Saving Throw: Neg.

Area of Effect: One creature

Components: V, S, M

Casting Time: 4 segments


The polymorph other spell completely alters the FORM and possibly the PERSONALITY of the recipient. Creatures of low INT cannot become smarter through this transformation; but may believe they have done so. Creatures of high INT, on the other hand may lose INT if transformed into a lesser form.

The creature polymorphed must make a "system shock" check to survive the transformation. If it does, it acquires all FORM-related abilities of the creature it has been polymorphed into. That is, if it has wings, it can fly. If it has teeth in a muscular jaw, it can bite to devastating effect. Thick scales will reflect in its AC. In fine, assess the new form in a mechanical way. Whatever that new form could do in a world WITHOUT magic, it can do, be it swim with fins, or trample with giant feet. But all abilities and powers dependent on magic or actual knowledge are NOT bestowed. Thus transforming a bug into an 18th level wizard, produces only a zero-level human that lacks any skills, powers, abilities or hp gained through training. Cf. DMG p.45

Although the polymorphed creature gains the FORM and mechanical abilities, HP are unaffected and remain exactly the same as they were prior to the transformation; so that a brontosaurus changed into an ant is very hard to crush, but an ant changed into a brontosaurus dies with a slap of the hand.

Lastly, the personality of the target will eventually change into that of the new creature. The chance of this happening is checked at the time of the transformation and once per day thereafter using the formula below:

100% - [Target’s INT x5] + [New Form’s HD – Original Form’s HD x5].

Should personality change, the polymorphed creature will behave as if it were the new creature, possibly attacking former friends and so on. Note that a creature who assumes the personality of a demon they have been polymorphed into may believe themselves capable of flight and might inadvertently hurl themselves to their death. A dog polymorphed into a red dragon might try to use its breath weapon only to come up dry and cough instead. The dog-red-dragon's AC would still be -1 and its bite would still be incredibly dangerous. It would still be able to fly. But its HP would remain the same as when it was a dog.

The magic-user must use a dispel magic spell to change the polymorphed creature back to its original form, and this too requires a "system shock" check. Dispelling the magic also restores the old personality if it was lost. Shapechangers (vampires, lycanthropes, druids, gods, dopplegangers, mimics, et al.) are immune to this spell. The material component is a caterpillar cocoon.

Feel free to discuss.

Peace, and happy gaming.

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