According to Polymorph's description,

The new form can be any beast whose challenge rating is equal to or less than the target’s (or the target’s level, if it doesn't have a challenge rating).

For example, a Tyrannosaurus Rex (MM, p81) is a beast with CR 8, 136HP, multi-attack, +10 attack modifier and a lot of damage.

Can a Wizard, at level 8, cast Polymorph on another PC (also at level 8) and turn him into a Tyrannosaurus Rex?

This sounds awfully broken. CR is usually measured against party level. A CR 8 enemy is meant to be a decent threat to a party of 4-5 PCs of level 8. We could find a ratio here, where each player accounted for 2CR (sort of...). But Polymorph lets one of the players actually equally face an enemy that could challenge the entire party.

I realize that there aren't any stronger beasts than the T-Rex, so the power-level doesn't grow, but it still feels like a spell that can easily break encounters. E.g., big boss fight incoming, some big baddie with a couple of helpers. The Wizards turns the out-of-spell-slots Bard into a T-Rex and then hides behind a pillar and inside a Minor Illusion Box. The T-Bard wrecks havoc among enemies while the party supports him and the Wizard is smoking his pipe hoping no one remembers he exists.

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    \$\begingroup\$ Can you elaborate a bit on the "easily break encounters" bit. If the players have these resources and want to use them to make an encounter easier, why is that a cause for concern? I guess I'm asking: why are you concerned if polymorph makes fights easier than planned? \$\endgroup\$
    – Adam
    Mar 17, 2017 at 14:46
  • \$\begingroup\$ Am I correct in assuming that your question is not "Can polymorph be used this way?" and is actually more in the lines of "Is polymorph used this way OP?" \$\endgroup\$
    – Sdjz
    Mar 17, 2017 at 14:47
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    \$\begingroup\$ @Sdjz Both, I guess. It was a "polymorph seems OP this way, can it really be used?" :P \$\endgroup\$
    – BlueMoon93
    Mar 17, 2017 at 15:02
  • \$\begingroup\$ Being a threat to a part of 4-5 PCs doesn't mean he's the equal of 4-5 PCs. Said PC before polymorph was about a CR 8 also. You didn't gain much. \$\endgroup\$ Mar 19, 2017 at 18:55

5 Answers 5



This may seem overpowered but there are several drawbacks to the spell:

The target's game statistics, including mental ability scores, are replaced by the statistics of the chosen beast. It retains its alignment and personality.

If you transform them into a T-Rex they become an unintelligent beast with an INT score of 2.

The creature is limited in the actions it can perform by the nature of its new form, and it can't speak, cast spells, or take any other action that requires hands or speech.

It can't communicate with you while in its new form or use its hands to activate any items, or otherwise perform any task that requires hands or speech.

The target's gear melds into the new form. The creature can't activate, use, wield, or otherwise benefit from any of its equipment.

It's AC changes to 13 (T-Rex is easy to hit but not easy to kill) making it an easy target from long range. It can't benefit from any magic items it might have or any armor or shields.

Also, the spell requires concentration. This carries two more drawbacks.

If the caster takes damage he or she must make a concentration check to maintain concentration. If it fails, the target reverts form which could potentially put them in a very bad situation, surrounded by enemies and perhaps with low HP (maybe polymorph was cast on the fighter when he was almost out of his own HP).

The other drawback here is the opportunity cost of concentration. The caster can't concentrate on any other spells while he is concentrating on polymorph, which means any other spells available to the caster that require concentration aren't available for the duration. This is a spell list that includes things like hold person, fear, suggestion, haste, slow, wall of fire, web, invisibility, greater invisibility, and levitate, to name only a handful of the concentration spells available to a level 7 wizard.

Consider also that beyond class level 7, there would be even more concentration spells available which might come at a higher opportunity cost than polymorph.

Furthermore, there is also the opportunity cost of learning polymorph. When you first gain access to it at level 7 as a wizard or sorcerer, you have 1 (sorcerer, bard) or 2 (wizard) spell choices available. Druid gets it automatically as they know all their spells -- crazy, right?

As a bard or a sorcerer at that level, you have chosen to forgo all other level 4 spells so that you can transform something into a T-Rex for one hour once a day (maybe more if you spend sorcery points). As a wizard, you have a little more flexibility. In any case, the opportunity cost of choosing this spell over any other spell should come with an appropriate value -- in this case, the ability to temporarily transform someone into a powerful beast and the versatility of being able to transform them into any other less powerful beast.

However, I think you're overlooking the more powerful use of polymorph -- the potential of turning any opponent of yours into a harmless chicken or goat while you take care of the rest of the goons trying to steal your gold. Removing a single powerful enemy from combat is a much better use of your action than creating a powerful ally, when creating a T-Rex leaves the powerful enemy on the table to make attacks against you and your other party members.

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    \$\begingroup\$ @nitsua60 Given the ludicrous offensive power of polymorph used on enemy targets, I'm not sure that's a strong argument here. \$\endgroup\$
    – Miniman
    Mar 17, 2017 at 14:56
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    \$\begingroup\$ Ah, you're saying the opp.cost of learning polymorph is super-low, because it's so useful both in transforming one's ally and in transforming one's enemy? Good point. \$\endgroup\$
    – nitsua60
    Mar 17, 2017 at 15:17
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    \$\begingroup\$ @Slagmoth That's not really a consideration for polymorph as you have the same problem whether you are or are not under its effects. Disintegrate is just a bad spell to be targeted by. \$\endgroup\$ Mar 17, 2017 at 15:37
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    \$\begingroup\$ @Slagmoth Actually, Disintegrateing a polymorphed target reverts him back either way \$\endgroup\$
    – BlueMoon93
    Mar 31, 2017 at 11:08
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    \$\begingroup\$ As any good Munchkin player knows the canonical use of polymorph is to turn the red dragon into a parrot and steal the treasure. \$\endgroup\$ Mar 16, 2021 at 17:16

Polymorph is no more broken than any other spell.

First, the full text of Polymorph.


This spell transforms a creature that you can see within range into a new form. An unwilling creature must make a Wisdom saving throw to avoid the effect. The spell has no effect on a shapechanger or a creature with 0 hit points.

The transformation lasts for the duration, or until the target drops to 0 hit points or dies. The new form can be any beast whose challenge rating is equal to or less than the target’s (or the target’s level, if it doesn't have a challenge rating). The target’s game statistics, including mental ability scores, are replaced by the statistics of the chosen beast. It retains its alignment and personality.

The target assumes the hit points of its new form. When it reverts to its normal form, the creature returns to the number of hit points it had before it transformed. If it reverts as a result of dropping to 0 hit points, any excess damage carries over to its normal form. As long as the excess damage doesn’t reduce the creature’s normal form to 0 hit points, it isn’t knocked unconscious.

The creature is limited in the actions it can perform by the nature of its new form, and it can’t speak, cast spells, or take any other action that requires hands or speech.

The target’s gear melds into the new form. The creature can’t activate, use, wield, or otherwise benefit from any of its equipment.

Right off the bat, we see some limitations to the spell. Your stats become 25,10,19,2,12,9. You become an unintelligent creature incapable of speech or strategy. Don't expect your T-REX friend to be helping you with flanking or focusing damage on the squishy caster.

Also, as a T-Rex, your rogue doesn't get sneak attack (no, a T-Rex is not sneaky), your cleric doesn't get to cast spells. It's arguable if your fighter even gets maneuvers or expanded crit range.

Also, remember this takes up a player. It's not like your party of 4 suddenly gets to add this massive 136HP, 13AC, 33 dpr, +10 to hit creature. You have to replace one of your existing players with this guy. A level 8 fighter has roughly 76HP, 18AC, 26 dpr, +8 to hit. So while it's an improvement, it's not a game breaking improvement. (Yes, you could target other party members. No, I'm not going to do all of them. It makes the point.)

So after considering the opportunity cost of turning one of your allies into a T-Rex, the comparative power of the spell goes way down. You could consider this as a +7 dpr, +2 to hit buff with some extra HP.

Now lets compare the opportunity cost of polymorph, by comparing it to other 4th level spells:

  • Banishment

    This one is especially useful if you are fighting a small number of powerful creatures. Charisma is normally a weak stat for beasts and humanoids, and is very rare ST to have proficiency in. Not only is it very likely to succeed, but you've just taken out (one of) the big gun(s) for up to 10 rounds. Do this on a final boss who is surrounded by minions, and you can mop up the grunts before having to face the big bad (just don't get hit).

  • Greater Invisibility

    Your rogue loves you for this one. Auto-disadvantage on attack rolls vs target makes up for how squishy melee rogues are. And totally eliminates the issues of "can I hide behind that tree and then pop out and attack before going back behind it again?" The rogue can now just bonus action hide, move 15 ft, attack, and repeat. Permanent sneak attack.

  • Vitriolic Sphere

    Here's a pure damage spell to compare to. Average of 37.5 damage on a failed save, 12.5 on a passed one. Slightly more damage, and slightly lower hit chance than a single T-Rex attack, but done to all creatures in a 20ft radius. That's 1256 ft^2, or 50 squares on a 5'x5' grid. If that's even 10% filled, you've done the damage of a T-Rex for 5 rounds and let your ally continue to do their own damage.

  • Aura of Life

    This one is only a Paladin spell, so 13th level rather than 8th, but same slot size, so worth the comparison. Now all friendly creatures within 30ft of you cannot die, unless someone hits them with 4 ranged or 3 melee attacks in a single round. Lasts 10 minutes, (w/ concentration), so it should go on for most of the fight.

  • Polymorph

    That's right, I'm comparing polymorph to polymorph. Because just like you can change one of your party members into a T-Rex, you can also turn one of your enemies into a snail. Finish off the rest (ala banishment), and then target that snail with a nice powerful attack. They're using the snails STs (including mental ones), so you're almost guaranteed to hit, and you can use that low accuracy, high damage attack to take a good chunk out of the big guy.

So all in all, while polymorphing an ally into a T-Rex might just be the most fun you'll ever have with polymorph, it isn't the most game breaking. You are loosing an ally when you do this, and creating a flesh eating machine. Additionally, there are other things that could also be useful which you could be doing instead.

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    \$\begingroup\$ "Now your DM will probably rule that to be less fun, and so let the polymorphed player continue to direct their polymorphed form at the bad guys, but they are perfectly within their right to enforce the "closest moving pile of food" rule for targeting creatures if they want. That could be bad news for your players." There's a stronger argument that since the character does retain their alignment and personality that they wouldn't turn on their party even if they do lose their intelligence. If any DM tried this I'd point this out first. \$\endgroup\$ Mar 17, 2017 at 16:12
  • \$\begingroup\$ @nitsua60 Good call. I admit that when I first saw this answer I quickly stopped reading because it was mostly quotes. It's often quite hard to read an answer that is mostly quotes. You have to read familiar material without knowing why it's here, then read the editorial text explaining the inclusion of the quote, and sometimes have to go back and forth between them to understand what point is being made. Repeat with each quote, and a wall of them is easily a turn-off for the reader. \$\endgroup\$ Mar 17, 2017 at 16:49
  • \$\begingroup\$ It is. I don't like having to go look up things, which is why I included them, but I didn't realize how big the answer got by the time I was finished. \$\endgroup\$
    – Shem
    Mar 17, 2017 at 18:41
  • \$\begingroup\$ Maybe create links next time? Best of both worlds, IMHO. The answer isn't a giant wall of quote blocks and people don't have to work to look it up, if they need to. Not even much more work for the person writing the answer. If you've opened up another page/tab to copy/paste the text, you've already done 95% of the work. That being said don't make link only answers! \$\endgroup\$
    – Shane
    Mar 17, 2017 at 20:00
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    \$\begingroup\$ @LegendaryDude Second this. Fido and Fluffy are no better than Int 2 and have no problem knowing friend from foe. Said T-Rex isn't going to turn on the party. \$\endgroup\$ Mar 19, 2017 at 18:48

Yes, he can, but speaking as a player who has a Wizard with Polymorph, it's not as impressive as you think it is. That player is effectively taken out of the combat as they can't use most of their class features. In addition, a T-Rex (or my favorite the Giant Ape) both have low AC and saves (note all of their stats mental and physical becomes that of the beast), so they are going to be giant damage sponges.

It's a decent spell that can turn your non-combat bard into a formidable foe, but most of the other players are better suited to being themselves with their full complement of abilities. Remember, it is a concentration spell so the wizard using this means that he can't also use haste or invisibility or any number of other spells.

It is a situational spell like any other and has its uses as a stalling tactic as it can effectively give 100+ temporary HP's to the tank while still keeping them combat ready, or alternatively, it can be used to defensively to temporarily take out the strong magic user, block them from casting spells by turning them into a rat.



The spell does what it says.

This sounds awfully broken.

A lot of wizard spells have the potential to be "broken." Depending on the situation banishment can work really nicely to snipe an encounter. Hypnotic pattern is, IMO, the most devastating impact-to-cost spell in the whole game. Leomund's tiny hut or even rope trick can snipe an entire dungeon by letting your party mates face most encounters fully-stocked. Heck, your L8 wizard can drop 5 fireballs during the day.

Polymorph is very versatile, very powerful, and very costly. Its costs are concentration + (all the other spells you could have cast with that slot) + (all the other spells you could have learned instead of it) + (all the other things you could have done had you been anything other than a Bard/Cleric/Druid/Sorcerer/Wizard). But it's not far out of line with a lot of other spells at that level.


While a CR X monster is a "challenge" for a party of 4 characters, a "challenge" means the party is going to win and nobody on the party is likely to die and the monster is going to die. The party will use up some resources.

A "deadly" encounter is 1.5 CR X monsters for a party of 4 characters. That is where the party is still likely to win, but there is a really decent chance a party member dies.

One could argue that an "even" fight, where it is a toss up who wins, is probably around 2 CR X monsters for a party of 4 level X characters.

The various advanced encounter building rules mostly have you add up the CR of monsters, divide by the number of players, and multiply by 4, with some small amounts of math fudging.

Afterwards, a value of 2/3 is "easy", 1.0 is "challenging", and 1.5+ is "deadly".

The exception is that you aren't supposed to use monsters with individual CR much above the party's level; this is probably because the spike damage gets out of hand.

But, based off those numbers, a level X character is "even" with a half of a CRX monsters, or is roughly CR X/2.

So Polymorph takes a CR X/2 player character and converts them to a CR X creature at the cost of concentration, until the CR X creature drops.

Using a limit of level/X would mean that polymorph, at the cost of a level 4, spell slot, gives you a separate pool of HP/resources to consume, without granting a significant boost in offensive power over not using it. If well chosen, it would grant a more appropriate form to the situation.

It is a very powerful spell. Unlike many spells, it gets more powerful as you gain levels, as it remains a level 4 spell slot for a target-scaling amount of effect.

A T-Rex is usually going to be much more effective in a combat than a level 8 Fighter; and when it drops you get your Fighter back.

If your DM is concerned about this, change it to something like:

The new form can be any beast up to CR 8, whose challenge rating is less than the target’s (or 4 plus half the target’s level, if it doesn't have a challenge rating).


At higher levels: The CR limit is twice the spell level, and the CR for creatures with levels is equal to the spell level plus half the target's level.

So a level 10 fighter could be polymorphed into a T-Rex (4+10/2 = 9, > 8) with a level 4 spell. A level 8 fighter can be polymorphed into a T-Rex (5+8/2 = 9, > 8) with a level 5 spell slot.

That slight delay in access to higher-CR forms, and increased cost to use higher-CR polymorph forms, should make the spell still strong and usable as a "buff", but not as crazy as it is right now.

  • \$\begingroup\$ Is your recomendation backed up by experience? \$\endgroup\$
    – BlueMoon93
    Apr 16, 2019 at 15:30
  • \$\begingroup\$ Not what I came for, but really good to know about the CR. Do you have any resources that back up the claim that a 2 CR X is a 'fair' fight given everyone is rested etc? \$\endgroup\$
    – findusl
    Jul 15, 2019 at 16:02

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