u/coldize

EDIT: I was wrong about how long turns and rounds lasted. Thank you for the corrections.
EDIT 2: Lively discussion! Loving it. I'm adding some exact wording rules to the bottom of the post that keep coming up.

Hey all, first time poster here and still somewhat of a novice to the game. I'm playing a Druid in my campaign and I just got access to this spell.

I've been digging into 5.5e mechanics a lot lately and trying to come up with some clever strategies and wanted to get some opinions on this one.

Here's the TL;DR:
Can I polymorph an enemy into a Giant Seahorse and just let it suffocate to death?

The Mechanics

Updated Polymorph rules:

• Crucial to this strategy: the target retains its own HP
• It gains some amount of Temporary Hit Points
• The spell ends early when the target has no THP remaining.

So now let's say I Polymorph a big bad enemy into a Giant Seahorse.
It has 16 THP, 5 Walk Speed, and it can only breathe underwater.

This means that, as long as it's on land, the Seahorse'd enemy has to hold its breath before it begins Suffocating:

>Suffocation [HAZARD]
A creature can hold its breath for a number of minutes equal to 1 plus its Constitution modifier (minimum of 30 seconds) before suffocation begins. When a creature runs out of breath or is choking, it gains 1 Exhaustion level at the end of each of its turns. When a creature can breathe again, it removes all levels of Exhaustion it gained from suffocating.
PHB (2024), pg. 376

A Giant Seahorse's CON mod is +0 so it can hold its breath for 60 seconds (10 turns of combat).
After that, they start accruing Exhaustion at the end of each of their turns.

>Exhaustion [CONDITION]
While you have the Exhaustion condition, you experience the following effects:

Exhaustion Levels. This condition is cumulative. Each time you receive it, you gain 1 Exhaustion level. You die if your Exhaustion level is 6.

Speed Reduced. Your Speed is reduced by a number of feet equal to 5 times your Exhaustion level.
PHB (2024), pg. 366

10 turns of combat isn't a lot, which means in most scenarios, this enemy can move 5 feet, maybe 10 total before they reach 1 Level of Exhaustion and their speed becomes 0.

Once they reach Exhaustion Level 1, they are completely helpless and immobile.

After 5 more levels of Exhaustion, they instantly die. The wording is clear.

• They do not lose all their HP
• Their HP is not set to 0
• They are dead

It only took 10 total turns of combat for them to begin suffocating, but it will take 6 of THEIR turns to outright die, which gives you plenty of time to finish up the rest of the combat and then decide what you want to do with them.

And hey, if you don't want to kill the enemy, turning them into a giant seahorse, making them watch as you defeat their allies, then standing over them as they nearly suffocate to death, letting them reach 5 levels of exhaustion, then breaking them out of Polymorph seems a pretty cruel and sadistic power move. That enemy would probably think twice about continuing to fight you.

I chose a Giant Seahorse because I didn't want to pick any form that had +1 or more to CON. 20 or more turns of combat before exhaustion sets in kinda takes the drama out of this. It also has enough THP to not get broken by chip damage (whereas a piranha or an octopus have 1 and 3)

Am I misinterpreting any part of this? What do you think of my polymorph strat?

EDIT 2: Here's some exact wordings from the PHB for some rules.

>DEAD
A dead creature has no Hit Points and can't regain them unless it is first revived by magic such as the Raise Dead or Revivify spell. When such a spell is cast, the spirit knows who is casting it and can refuse.
PHB '24 pg 24 - Damage and Healing

>Falling Unconscious
If you reach O Hit Points and don't die instantly, you have the Unconscious condition (see the rules glossary) until you regain any Hit Points, and you now face making Death Saving Throws (see below).
PHB '24 pg 365 - Rules Glossary

>Temporary Hit Points
Some spells and other effects confer Temporary Hit Points, which are a buffer against losing actual Hit Points.... THEY'RE NOT HIT POINTS OR HEALING
PHB '24 pg. 29

I think we can infer from this that to have any THP, you must have HP. If you die, you no longer have HP.
If you don't have HP, you can't have a buffer against your HP, and so you no longer have THP.

Not having THP is a condition that ends Polymorph.

So you would revert back to your original form, still dead.

If I were WotC: I get that this does toe the line about spirit of the game, and if I were WotC, the rule I would add to combat this would be that when you reach Exhaustion Level 3, you lose any THP you currently have and can no longer benefit from it. Boom, "loophole" fixed without outright gutting the strength of the strategy.