How is True Polymorph not completely unbalanced?

Question

How is True polymorph balanced in regards to any spell besides Wish? (Which is inherently unbalanced per design).

Two example uses that seem unbalanced:

• A level 20 Warlock and Bard are having a talk about dragons, and the bard comes up with the idea of becoming a dragon. The warlock casts True Polymorph, turning the bard into an Ancient Brass Dragon (possibly even one that can cast spells). After the hour-long concentration is completed, there is an Ancient Brass Dragon in the party that can kill basically anything it wants and shapeshift back into his Lvl 20 Bard self and play a jaunty tune while he's at it.

• The Warlock and Bard are battling a powerful Lich, and the Lich gets turned into a frog. It wouldn't be dead, so its phylactery would be useless. It would gain the intelligence of a FROG, meaning that the threat has been nullified as long as the frog lives. Maybe they could make it a tortoise for good measure. That leaves the party, or others, 100 years to find its phylactery and do away with it, no rush necessary.

I know there are other questions about this spell and how it works, but my question is: How can you balance this spell, without taking away the RAW, or the power of the players?

Answer 1

1. That isn't how Change Shape works

...there is an Ancient Brass Dragon in the party that can kill basically anything it wants and shapeshift back into his Lvl 20 Bard self and play a jaunty tune while he's at it?

Change Shape for a Brass Dragon includes this caveat at the end of the description (MM p. 104):

Its statistics and capabilities are otherwise replaced by those of the new form except any class features or legendary actions of that form.

He doesn't turn back into his bard self, since he can't take on the Class features. There are reasons for this.

• His new self is the Brass Dragon, not the humanoid Bard. That's what the permanent feature of True Polymorph does ... you become something new.
• Player Characters and Classes don't have a CR, and CR guides what you can turn into. (Or level, if the target doesn't have a CR)

A related consideration is: what age group of a dragon do you turn into? Is it related to character age, or not? The discussion in that question about Dragon PC's may be of interest to you.

As for the Lich being turned into a turtle? Good idea, if you can manage it.

2. Balance and 9th Level Spells

By the time characters can use 9th level spells, balance becomes a function of DM style, choice, and rulings. Spells of that level are very, very powerful, in some cases making changes in reality of the game world. True Polymorph and Wish are particularly good examples of that. Characters at levels 17-20 are in the "Masters of the World" level of adventure as described in the DMG page 37. (Cue Crosby, Stills, and Nash singing We can change the world) Game balance at this point comes from DM challenging the players and DM rulings.

OK, so you're the DM, and ask "How do I balance this?" At that level, adjusting the level of challenge for your players is where you find the balance point. That's part of your role as DM. Bounded accuracy in 5e is one limit to player power. Increasing the challenge by increasing the numbers and kinds of opponents, or creating unorthodox alliances of NPC's and monsters is a way to keep the players challenged at high levels.

If the players are warping reality too far in one direction, the arrival of a pair of silver dragons(ancient), a few high level high celestials / angels, and a few NPC's to challenge them isn't out of line.

Another line to explore is that your new Ancient Brass Dragon PC has become the challenge to be overcome by a party of high level adventurer NPCs. That's what high level adventurers do, it seems: slay dragons.

A further limitation, and potential balancing method, on this use of True Polymorph is in the published errata (for the sixth printing of the PHB, and in the spell's text in the SRD, V 5.1): the "permanent" feature of true polymorph lasts until it is dispelled. If some opponent or nemesis of the PCs learns that the PC had been true polymorphed into dragon form, a casting of Dispel Magic (at 9th level, or with a successful DC 19 check if cast at a lower level) would return the bard-dragon into the bard's original form. That's a way to "balance" the magical effect if the bard-turned-ancient-dragon creates an unbalanced situation in a given campaign. (Thanks to @guildsbounty for the update)

The only limit to the challenge is the limits of your imagination. There is a load of help for the DM in the DMG. It covers a very broad range of tools to help the DM create a challenging game world.

Answer 2

Most spells aren't "balanced" when you apply them in a vacuum.

Spells seem very powerful when you create a hypothetical situation where the effect just happens. For instance, in the second example you provided, a few things happened without you mentioning them:

1. The Lich failed his save. I should mention that this is incredibly unlikely.
2. The Warlock didn't expend all of his spells before reaching the final encounter. This may or may not happen, depending on whether or not the party knows they'll be fighting a Lich, and depending on what kind of encounters they meet along the way.
3. The Warlock didn't get killed or incapacitated by a previous encounter, or get level drained by a trap, or get silenced during the encounter, or anything else that would prevent him from casting the spell at the right time. These are all reasonable things that can easily happen when you're at proper level to be fighting Liches -- the kid gloves should be off now.

Wish offers some nice benefits, but most of the safe ones are one-upped by magical items, namely the stat bonuses. Truly world-impacting effects are possible, but liable to be twisted (which is arguably encouraged by the book) by the GM through semantic loopholes. Effectively, wish allows the caster to be GM for a moment... except the change he makes is still vetoed by the actual GM. The game is only ever as "unbalanced" as the GM (and by association, the players, ideally) wants it to be.

Keep in mind: the GM is effectively the one true God of your fantasy universe

When the game gets to high level play, the GM has more responsibility, in my opinion, because it's much easier for the players to get what they want. Not only should the players get better at playing the game as their characters level up, but the GM should also get better at GMing. If true polymorph is making the game too easy, then the game will suffer, not just for the GM, but the players also. With rare exceptions, people don't want to play games where there's no challenge. It's the GM's job to make sure that you are challenged once you get access to true polymorph, and the game provides tools to do that without the dreaded GM fiat.

Answer 3

1. According to Jeremy Crawford, if the result of a PC being permanently changed into something is burdensome to either the player or the DM, the character becomes an NPC and the player must create a new character. This should discourage such behavior.

2. A lich has legendary resistance and advantage on saves for this exact reason. By this level of play, a lich is easily defeated by any number of spells, IF you can get it to fail a save. Lich fights are always fast and furious, whichever side wins.

Answer 4

Well, as a DM, I would look at case 1 as impossible, Ancient Brass Dragon is an age group, not a different version of a monster. To my mind, if the bard was, say 50 years old, he would be a 50 year old brass dragon, with all the bonuses and penalties therein. He would be far too young (IMHO) to be a spellcaster, and that that age, he would be fodder for any group of good players in the 3-5 level range. Not quite what he had hoped for during the polymorph. That is, of course, my humble opinion on how to GM that. It all comes down to the fact that ancient is an age group and not a different 'type' of critter.

As for #2, no self respecting Lich would fail the spell save and then the Wisdom check :) But then again, A lich fighting a group that has level 20 characters is in for a rough ride, no matter how well he rolls. A group of 20s should be able to whup up on a Lich in many ways.

It all comes down to DMing the effects of spells to make sure the players have fun, but not ruin the game for everyone. If your party all wants to be shapeshifting young dragons (for the flying fun) and you can handle it, let them do it. If you don't want to deal with it, there are many ways to make it a bad deal. (and a great adventure to remove the permanent shape shift as well :)

Answer 5

Itt literally says in the game (for the people saying that you can't turn a level 20 character into an ancient brass dragon):

Creature into Creature. If you turn a creature into another kind of creature, the new form can be any kind you choose whose challenge rating is equal to or less than the target’s (or its level, if the target doesn’t have a challenge rating). The target’s game statistics, including mental ability scores, are replaced by the statistics of the new form. It retains its alignment and personality. (Spell Description, True Polymorph)

That if it is a person that has levels and not CR that means they can become a monster that has a CR equal to their level. A level 20 player character can become a CR 20 ancient brass dragon.