D&D 5E (2024) Need a recommendation for polymorphing enemies

[ECMO3]

So I am having the final boss fight this week in a 20th level campaign (my PC is a Fighter 12/Warlock 8). The end boss is a wizard Undead. Think Lich but substantially more powerful and two minions, one a Fighter type the other a Cleric type.

I have a scroll with a custom spell from the DM, it is a 10th level spell called Mass Polymorph. It works like a regular Polymorph but it can affect up to 10 creatures. I will need to roll a DC20 Charisma check to cast it, but I have a 26 Charisma and tactical mind and an inspiration, so I will probably make the Charisma check.

If I use the scroll I will turn party members near death into T-Rexes (or at least anyone that would benefit from it at the time) dishing out 100+ temp hit points to everyone. For the enemies I figure I want to go with something that has a swim speed but no walking speed and a lot of hit points with preferably a weak attack. The best I can think of is a Reef Shark. Then they would be immobile and flopping on the ground. I am worried though that any non-polymorphed bad guys will just drain the temp hit points to end the spell on them.

Any ideas on a beast with decent hit points, weak attacks and preferably no walking or flying speed?

 

[humble minion]

Giant Snail, from Witchlight? Only 22hp though, same as a reef shark, so might not be enough for your purposes.

 

[MarkB]

Killer whale? Nasty attack, but only 5 ft walking speed and 90 hp.

Alternatively, throw in a bag of rats and cast it on them to turn them into T-Rexes, then wait while they fight it out with the bad guys and go in afterwards.

 

[MonsterEnvy]

Turn enemies into normal Turtles and then just leave them alone until you deal with the active enemies

 

[bedir than]

Intending to turn the opposition into big HP options makes this a bit more difficult.

My players turned an opponent into a knucklehead trout - which satisfies all of your guide rails except the HP.

The Sperm Whale is in Rime of the Frostmaiden. It makes the Killer Whale feel small.

 

[AlViking]

Intending to turn the opposition into big HP options makes this a bit more difficult.

My players turned an opponent into a knucklehead trout - which satisfies all of your guide rails except the HP.

The Sperm Whale is in Rime of the Frostmaiden. It makes the Killer Whale feel small.

The problem with turning enemies into fish is that they suffocate and then turn back. So I agree with @MonsterEnvy on the turtle thing, or perhaps something even smaller and slower like a snail. Although if you do turn them into snails make sure nobody paints a letter on the side, you may be amazed at how fast the S car go.

 

[bedir than]

The problem with turning enemies into fish is that they suffocate and then turn back. So I agree with @MonsterEnvy on the turtle thing, or perhaps something even smaller and slower like a snail. Although if you do turn them into snails make sure nobody paints a letter on the side, you may be amazed at how fast the S car go.

Sperm whales hold their breath for 90 minutes.
If the fight is lasting that long there's a bigger problem than "turtle or seaborne mammal"

 

[MarkB]

Sperm whales hold their breath for 90 minutes.
If the fight is lasting that long there's a bigger problem than "turtle or seaborne mammal"

Whales aren't fish, so they don't need to hold their breath. I think it was more the trout example that was being called out.

 

[Clint_L]

Thought on turning your party into T-Rxes: that makes them pretty dumb, which could be a problem both for saving throws and for tactical planning. Maybe giant apes, instead; similar HP and attacks, but Intelligence 7? Also, having opposable thumbs can turn out to be useful.

 

[AlViking]

Sperm whales hold their breath for 90 minutes.
If the fight is lasting that long there's a bigger problem than "turtle or seaborne mammal"

A sperm whale doesn't need to hold it's breath outside of water because they aren't fish.

I guess you could turn them into something with a decent amount of HP means it's less likely to revert back when it's temp HP go away. On the other hand their sudden increase in size could cause other difficulties.

The real question is whether or not it needs to be transformed into something that we have stats for. Some DMs would not want a turtle because they'd have to make on the spot decisions.