D&D 5E True Polymorph - Too powerful?

[Maxperson]

The thing is it says it keeps its personality and alignment. Raw it should work right?

Personality is not intelligence or ability to think like your old self. Personality is jolly, angry, depressed, and other things like that. I don't care how jolly or good you are, if someone is cutting of your heads you're going to fight back.

 

[pogre]

Also Ben kept making jokes about giving my wife and "giving head" because haha hydra. My wife seemed to find it funny so I don't want to be a sour sport.

This is potentially the much larger issue than some spell in a fantasy game. I don't want to read too much into this, but I see no harm in saying, "Hey Ben, it was mildly amusing the first time, but now that joke is starting to annoy me. You want to lay off please?" If he is your friend he should respect that. If not, like I said, you have larger issues.

As for polymorph - no, I would not ban it. Given enough time and preparation a high level party should win a fight easily. If winning is important to them - give them the win and move on. If the play is more important to them - find a way to have your BBEG escape or even counter the polymorph.

 

[MarkB]

Well, hydrawizard is huge, so very limited as to where it can actually get to, and honestly if it's got that many heads I'd definitely bump its size up to gargantuan, so now it's strictly an outdoor wizard.

It's still only got 30 feet movement, though obviously that can be buffed, so any reasonably mobile foe can just maintain distance.

And if it comes up against anything with immunity to non-magical piercing damage, it's completely and utterly ineffectual.

 

[Torquar]

Give the BBEG an inflicts damage on hit effect like Fire Shield or Shadows of Moil. Hydra will likely kill itself before the BBEG.

 

[AtomicPope]

I gave my players 1 day to prepare for a final boss fight that we are having next week. They have a lot of resources from nearly saving a continent. One player true polymorphed into a hydra and all they have been doing is cutting and re-growing heads and healing. It now has 1069 heads after we did the math on how long they have. I am worried that next week they will just kill the BBEG with 1069 attacks in one turn. Do you guys ban true polymorph in your game to prevent this from happening?

What would you do here. I don't want to ruin any friendships. I'm thinking of banning true polymorph from future games.

Thanks for the help!

There's a couple of things happening here that are important:
1) If the polymorph lasts for the entire duration, it's permanent.
2) Concentration can be broken. A hydra fights back. If it breaks concentration then you lose your 9th level spell.
3) Mental changes occur. Hydras are not friendly, even when you chop their head off for a good reason. You'd need to Dominate Monster.
4) Truesight (and Witchsight) reveals shapechangers. This opens the door to removing True Polymorph and ruining the surprise.
5) Disintegrate destroys True Polymorphed creatures. They do not revert back. That often comes as a surprise to shapechangers.

I bring these up because in an Epic campaign my 20th Level Warlock disintegrated a Shapechanger, much to the surprise of the DM. The only stipulation for reverting back is from hit point damage. True Polymorph does not prevent death effects. Finger of Death would do the same. It kills the target when they reach zero hit points. No save. Do not pass go. Do not collect 200 electrum. Big monsters like Hydras have notoriously low Dex saves.

 

[Shiroiken]

True Polymorph is a 9th level spell, on par with Wish, so it should be awesome. As others have pointed out, there should be some limitation on the ability to manipulate the hydra. Additionally, each time they're hit to grow a new head should create a Con save to maintain concentration, which should significantly reduce the probability of success. Even if they happen to succeed, there are ways the BBEG and prepare to stop it.

If the BBEG isn't a caster, give them a way to have Antimagic Field; this will significantly hamper the party, as the melee characters will have to damage him enough to break concentration first. If the BBEG is a caster, and they should be for this high level a combat (or at least have minions that can cast), the following spells should take care of the mega-hydra: Maze, Forcecage, Psychic Scream, and for a cruel twist Dominate Monster. Worst case scenario, you can force a small passage to get to the BBEG, preventing a huge creature from getting through.

 

[Lyxen]

It's not an easy situation, and it's really not about finding technical solutions, tons of them have already been suggested (both good and bad from my perspective, see below why).

It's about your players clearly abusing rules which are simple and made to be controlled by the DM - which you let them do, apparently for a while if they had time to do that kind of computation, and which they enjoyed - in order to produce a silly result.

So, at this stage, you have only a few choices probably along the following spectrum:

1. Let the plan succeed, tell them that the hydra successfully devours the BBEG and that it's an epic end of the campaign (no need to roll and play it).
2. Let the plan succeed to a point, tearing down some of the BBEG lair's defenses, maybe even killing the first form of the BBEG (make him a mythic monster)
3. Tell them "guys, that was fun, but there is no way the hydra body will be able to move around that many heads anyway, and no way the BBEG will let himself be cornered by such a huge monstrosity to be easily slaughtered", let's get serious if you want a truly epic fight at the end of the campaign.
4. Do not tell them anything, but design the BBEG and his lair so that the Hydra plan does not work (So many ways, BBEG flying, too narrow corridors, killing traps, deadly spells for a stupid walking hydra with low saves, etc.).

Before you make your choice, seeing how your players behave, I think that you also should take a moment to reflect on this with your players for the next campaign, because the problem is not really true polymorph, it's the way you let them go down a path that led to abuse of the rules, so it's about the table's expectations and your DMing style.

That being said:

1. is the best way not to be a sourpuss, but then you really need to set things straight for the next campaign. After all, if this is what your players enjoy for the end of the campaign, let them have what they want, why should it be a problem to you ? But then expect that this will be repeated often in further campaigns. There is nothing wrong with that play style, it encourages creativity and it can be a lot of fun, just be aware as a DM of what you are doing and why.
2. That would be my preferred choice for my players (but it does not mean that it is for yours), it makes their planning meaningful, but it still leaves room for an epic fight.
3. That is also a good choice, as it appeals to some maturity for your players and helps them think maybe a bit more solidly about what they might want in their games, but it invalidates their planning and what they did might just be the way they want to play, so it's really up to you whether you want this discussion now or before the next campaign or actually never.
4. Is probably the worst choice as it really invalidates what they did without any explanations, which is why some of the suggestions of other posters are for me not really good.

So, it's really up to you, happy to discuss further if you give us more details or want more feedback. Good luck !

 

[MarkB]

True Polymorph is a 9th level spell, on par with Wish, so it should be awesome. As others have pointed out, there should be some limitation on the ability to manipulate the hydra. Additionally, each time they're hit to grow a new head should create a Con save to maintain concentration, which should significantly reduce the probability of success. Even if they happen to succeed, there are ways the BBEG and prepare to stop it.

The spell only requires concentration for its one-hour duration, and they've cast it a day in advance. At this point, it lasts until someone dispels it or until the hydra form is reduced to 0 hit points.

 

[see]

I mean, it might be overpowered in this specific scenario, given the full factors of your campaign. But as a general rule, something that can be knocked out by a single good roll with a 3rd-level spell (true polymorph only lasts until dispelled) is not overpowered for Tier 4 play.

 

[Maxperson]

There's a couple of things happening here that are important:
1) If the polymorph lasts for the entire duration, it's permanent.
2) Concentration can be broken. A hydra fights back. If it breaks concentration then you lose your 9th level spell.
3) Mental changes occur. Hydras are not friendly, even when you chop their head off for a good reason. You'd need to Dominate Monster.
4) Truesight (and Witchsight) reveals shapechangers. This opens the door to removing True Polymorph and ruining the surprise.
5) Disintegrate destroys True Polymorphed creatures. They do not revert back. That often comes as a surprise to shapechangers.

I bring these up because in an Epic campaign my 20th Level Warlock disintegrated a Shapechanger, much to the surprise of the DM. The only stipulation for reverting back is from hit point damage. True Polymorph does not prevent death effects. Finger of Death would do the same. It kills the target when they reach zero hit points. No save. Do not pass go. Do not collect 200 electrum. Big monsters like Hydras have notoriously low Dex saves.

The bolded part isn't true with the spell. The spell specifically keeps alignment and personality, so the new hydra wouldn't need dominate monster unless the one being changed was mean or an evil cuss. A good PC would be like a dog. It would be loyal, perhaps kind, good, etc. What it wouldn't be is smart enough to understand the plan, so if they start cutting off its heads it would turn right quick and fight back like any animal would if you were killing it over and over.