What does it take to kill a Tarrasque? We ran the numbers.

The Tarrasque is CR 30, and calibrating a fight against it is hard. So we ran the numbers in a simulator that plays every fight turn by turn under the 2024 rules: every attack, save, spell, reaction and legendary action. The parties were level 20, using the free-rules classes, with no magic items and no cheese tactics. Each party fought 120 times.

A few things that surprised us:

Four heroes never win. Not once in 120 fights, and every hero dies. Six heroes win 90% of the time. Seven win every fight.

Who you bring matters as much as how many. A Barbarian or a Monk as the sixth hero beats the standard party. Leave the Cleric at home and you win only half your fights.

Sword-swingers struggle. It resists weapon damage, magic weapons included, so the Fighter deals less than the Rogue. Irresistible Offense fixes that for the Fighter and barely matters for anyone else.

Casters have it worse than you'd think. It's immune to fire, its carapace stops attack-roll spells five times in six, and it saves with advantage. Our fire-built Sorcerer's Metamagic doesn't save it; Power Word Kill would.

Full write-up, with charts and a replay of one of the fights you can watch round by round:

https://longtabletools.com/blog/what-does-it-take-to-kill-a-tarrasque

If you've run the Tarrasque at your table, I'd like to hear how it compares. 

This is really cool! Thanks for sharing! I feel like I'm on the right track building a character that focuses on radiant and force damage

What this article fails to cover is ingenuity. The party only goes for damage, and the machine seems to not plan for future turns by whittling down legendary resistances before using a killer save-or-suck, a common tactic. It also only utilizes the SRD subclasses, which you cannot really fault them on, but nearly any other subclass does better than the SRD ones.

I'd take a Divination Wizard, Echo Knight fighter, Elements or Ascendant Dragon Monk, Twilight or Peace Cleric, Arcane Trickster Rogue, and a Noble Genies Paladin. That'd make the fight much smoother.

Quote from Tunyci >>

Leave the Cleric at home and you win only half your fights.

 

Clerics rule.  Just sayin'. 

Not having any magic items is... rather implausible (being limited to the basic rules, and thus not getting access to things like great weapon mastery or sentinel, is also crippling). The numbers would have at least somewhat more connection with reality if you used starting at higher levels. For simplicity, use a +3 weapon as the Very Rare for barbarian and fighter (there are better choices against the Tarrasque, such as a Sun Blade, but it's a credible baseline). This increases their attack bonus from +11 to +14 (matters more for the fighter than the barbarian, as they don't have 100% reliable advantage).

For Rare items, give them a consumable, such as a potion of Giant Strength, Heroism, or Invulnerability.

Casters don't really have as wide a range of things that empower them and will thus benefit less; typically they will want defensive or mobility options.

Of course, the big problem with the Tarrasque has never been its brute power, it's that it's entirely incapable of dealing with even very basic tier 4 cheese.

Having a 150 ft cone AoE offsets a decent chunk of the cheese. Also, a Tarrasque has never been something intended to be fought in a remote boss arena- the 2024 MM literally gives “Urban” for its environment. It’s a kaiju meant to roll up on a city and force the party to deal with it before it levels the place- note that the aforementioned AoE specifically affects objects and is covered by the Siege Monster trait for double damage on structures.

Quote from The_Ace_of_Rogues >>

Having a 150 ft cone AoE offsets a decent chunk of the cheese. Also, a Tarrasque has never been something intended to be fought in a remote boss arena- the 2024 MM literally gives “Urban” for its environment. It’s a kaiju meant to roll up on a city and force the party to deal with it before it levels the place.

The Tarrasque playing Godzilla is much easier to kill than if it were in a remote boss arena. The main thing that blocks cheese in the 2024 version is that it has Burrow speed. In general the Tarrasque is poorly designed enough as a monster that you're probably going to cheese it accidentally.

Quote from MongooseGef >>

This is really cool! Thanks for sharing! I feel like I'm on the right track building a character that focuses on radiant and force damage

 Glad you liked it! Yes, those are great ways to get around the damage resistance! Good luck!

Quote from EdgohSaile >>

What this article fails to cover is ingenuity. The party only goes for damage, and the machine seems to not plan for future turns by whittling down legendary resistances before using a killer save-or-suck, a common tactic. It also only utilizes the SRD subclasses, which you cannot really fault them on, but nearly any other subclass does better than the SRD ones.

I'd take a Divination Wizard, Echo Knight fighter, Elements or Ascendant Dragon Monk, Twilight or Peace Cleric, Arcane Trickster Rogue, and a Noble Genies Paladin. That'd make the fight much smoother.

Thanks, I agree! The article is purely informed by the simulator which does handle the breaking down of legendary resistance. It can happen but only occurs very rarely (big T has a lot of them!). 
Your point about those other subclasses are spot on! This piece was really just about the basic classes.

Quote from Pantagruel666 >>

Not having any magic items is... rather implausible (being limited to the basic rules, and thus not getting access to things like great weapon mastery or sentinel, is also crippling). The numbers would have at least somewhat more connection with reality if you used starting at higher levels. For simplicity, use a +3 weapon as the Very Rare for barbarian and fighter (there are better choices against the Tarrasque, such as a Sun Blade, but it's a credible baseline). This increases their attack bonus from +11 to +14 (matters more for the fighter than the barbarian, as they don't have 100% reliable advantage).

For Rare items, give them a consumable, such as a potion of Giant Strength, Heroism, or Invulnerability.

Casters don't really have as wide a range of things that empower them and will thus benefit less; typically they will want defensive or mobility options.

Of course, the big problem with the Tarrasque has never been its brute power, it's that it's entirely incapable of dealing with even very basic tier 4 cheese.

Yes, those were somewhat strict limitations I started with. I'm planning to re-run an updated version with magic items as well.

Thanks everyone for commenting! 

Since then I added a new feature: you can actually play the battles turn by turn as in a tactical videogame.

Click here to challenge yourself with article's four heroes against Big T (this should not be easy!):

 https://longtabletools.com/tools/challenge?p=171081376,171082076,171083596,171083152&m=tarrasque&at=gladiator-arena&seed=625162

Btw, you can import your own characters as well (though some of their rules may not be fully supported instantly). You can also change the arena to other maps that I have on the site. Give it a shot if you feel like it! Feedback is very welcome!

It seems to me that everyone is missing the very thing that makes the Tarrasque such a terrifying monster. You're all examining nothing more than the mathematics of combat turn efficiency. Everyone is trying to calculate which subclass combinations have the best chance to overcome the stat block of the Tarrasque. Not only is that extreme metagaming, it completely ignores what makes the Tarrasque so deadly.

One of you nearly got there. You mentioned that the Tarrasque's terrain type is Urban. You're not going to fight this thing in an empty field. You're not going to fight it in a closed arena. It's going to appear in a city and you're going to have to fight it in a city. This is the Avengers at Sokovia. Everything you do to hurt the Tarrasque also risks hurting innocent people. Every round that you don't kill it, it kills dozens if not hundreds of innocent people. You're not just dealing with one monster. You're dealing with difficult terrain, and you're dealing with thousands of screaming panicking people. Have any of you ever been in a panicked crowd in a crowded city? Sure, your Str-20 barbarian may be stronger than any civilian, but when fifty panicking civilians need to get past you, they will. You're not just in danger of being trampled to death by the Tarrasque. You're in danger of being trampled to death by the very people you're trying to save! 

The Tarrasque is not a combat dilemma.  The Tarrasque is a MORAL dilemma!  It forces you to decide how much collateral damage is acceptable. It forces you to decide which innocent civilians you can save and which innocent civilians you need to let die in order to maintain your tactical advantage.

You can plug all the numbers you want into a spreadsheet until the computer grants you victory, but that won't make you heroes. 

Just my 2 c.p.

Quote from AnzioFaro >>

It seems to me that everyone is missing the very thing that makes the Tarrasque such a terrifying monster.

 The Tarrasque is an attempt to create a monster that you can run like Godzilla. It fails at its fundamental task, because if you actually have the Tarrasque being this slowly approaching terror, it gets intercepted in the middle of nowhere and turned into a pincushion. Sure, you can have it be this weird tunneling thing that surfaces in the middle of a city and makes a mess, but that's failing at the basic Kaiju task.

Why does it necessarily get intercepted in the middle of nowhere? Keep in mind when you account for Dash and Legendary Actions it can move 240 ft per turn, and between 25 AC, about 700 HP, Magic Resistance, and 6 LRs it can pretty reasonably endure several volleys from even high tier PCs without being distracted from whatever it’s moving towards and leave the party struggling to catch up.