can I use this as proof 

Quote from Capt740 >>

The true terror of the Tarrasque is not its stat block or abilities, nor is it its combat potential. No matter what you do, the Tarrasque won't stay dead. Even the wish spell cannot keep a Tarrasque dead for long. It will ALWAYS regenerate from the largest remaining piece of it, even if that piece is a sub-atomic particle. It may take days or weeks but it WILL regenerate. No god or magic weapon can truly kill the Tarrasque for good.

Also the Tarrasque's stomachs are the only things in the multiverse able to permanently kill gods and destroy artifacts. When you enter the Tarrasque's third stomach, you cease to exist, no magic, no divine intervention, nothing can save you or bring you back. 

Tiamat, and even some CR 23+ creatures, can 1v1 crush the Tarrasque any time they fight, for the rest of eternity. But the Tarrasque only needs to win once, and they can't get rid of it. 

The only thing that can permanently kill a Tarrasque, is another Tarrasque. That's why there is only one.

 

Also I'm pretty sure the Tarrasque doesn't care if you're immune to non-magical damage, if its stomach can erase gods and destroy MAGICAL artifacts that are typically INDESTRUCTIBLE, then there is no way you are surviving just because you're immune to non-magical damage.

 where did you get that information? 1e

In the 5e MM it says nothing about the tarrasque being immortal and its swallow attack doesn't say "Oh if you get swallowed you die" it says "Swallow. The tarrasque makes one bite attack against a Large or smaller creature it is grappling. If the attack hits, the target takes the bite's damage, the target is swallowed, and the grapple ends. While swallowed, the creature is blinded and restrained, it has total cover against attacks and other effects outside the tarrasque, and it takes 56 (16d6) acid damage at the start of each of the tarrasque's turns. If the tarrasque takes 60 damage or more on a single turn from a creature inside it, the tarrasque must succeed on a DC 30 Constitution saving throw at the end of that turn or regurgitate all swallowed creatures, which fall prone in a space within 10 feet of the tarrasque. If the tarrasque dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 30 feet of movement, exiting prone." also Tiamat is immortal via "Discorporation. When Tiamat drops to 0 hit points or dies, her body is destroyed but her essence travels back to her domain in the Nine Hells, and she is unable to take physical form for a time."

Quote from KthunkTheBarbarian >>

I'm back! Elder Brain Tarrasque stats! yay!

 

 I like it but maybe add some extra psychic damage to the attacks other than tentacle.

Given a Tarrasque has a very long lifespan, is there any reason that one could not gain intelligence?  After having spells cast against it, it starts thinking about spells and over the decades buried in its burrow it slowly gains some spell ability?  Dragons have young to ancient stats so why would a Tarrasgue have a never changing statblock over a nearly immortal lifespan?

Quote from James49478 >>

Given a Tarrasque has a very long lifespan, is there any reason that one could not gain intelligence?  After having spells cast against it, it starts thinking about spells and over the decades buried in its burrow it slowly gains some spell ability?  Dragons have young to ancient stats so why would a Tarrasgue have a never changing statblock over a nearly immortal lifespan?

 Simply put: it's never had to. The tarrasque spends 99.99999999999999999999999% of it's time asleep and then wakes up and binge eats for a couple weeks all of the biomass in a given area before burrowing under the ground and sleeping off it's transfinite carbs.

Also, the Tarrasque is pretty dim-witted.

Yes, the Tarrasque would get bodied by so many creatures and player types, and I realised this a long time ago, and since i really wanted a large brute-beast, i made the tarrasque a true titan... something to REALLY be feared... so, I present to you

Tarrasque, True Titan



Though after reading all this cool lore and stuff from 1e, i might wanna bring it back for my revamped version of the tarrasque.

Now i'd like to ask a question. Who would win in a fight.

Tarrasque, True Titan?

Or any version of Tiamat.

 Tiamat wins.  Super-Tarrasque still can't do a think about flying enemies that don't come within its reach, so she can simply spam lightning, cold, and acid breath weapons at it with impunity.

Quote from 6thLyranGuard >>

 Tiamat wins.  Super-Tarrasque still can't do a think about flying enemies that don't come within its reach, so she can simply spam lightning, cold, and acid breath weapons at it with impunity.

Well, a stalemate is probable, since it has regeneration and evasion with a +22 dexterity save. It also doesn't do anything about the 'boring' part of the tarrasque.

Cant it stun with its Thunderous bellow? And can't it reliably go before Tiamat? Surely that's enough to tip the edge?

Of course Tiamat can woop the Tarrasque with enough prep-time like batman

Edit: Im very aware Tarrasques are kinda boring. (Actually pretty boring), like most simple beasts or monsters, they're simply just big creatures, which is why we love to make them accessories to the main villain. This Tarrasque isnt trying to break out of the norm or be unique, this Tarrasque is trying to be a cataclysmically powerful version of those boring beasts to use as a dumb, huge, accessory.

If you want super cool flavor, versatile, and fun beasts or monstrous creatures to play as? Displacer Beast's are great, any sphinx really,


or... You could my statblock for the Terrasque, and then use the Elder brain Terrasque statblock and merge it into one terrifying creature.

Quote from SentientSteel >>

Cant it stun with its Thunderous bellow? And can't it reliably go before Tiamat? Surely that's enough to tip the edge?

Anything resembling stealth is missing from its stat block. In any case, sure, bigger numbers can win, but it's not a particularly useful exercise in monster construction, and this thread is actually about a good boss, not about a powerful boss.

That is fair, but don't people have general knowledge on how to make a good boss fight?

1 Memorable
2 Exciting
3 Good Climax
4 Resolves Part of the Story or all
5 Challenging

The Terrasque doesn't do all of that; a good boss fight would more likely come from Tiamat.

Quote from SentientSteel >>

Cant it stun with its Thunderous bellow? And can't it reliably go before Tiamat? Surely that's enough to tip the edge?

Of course Tiamat can woop the Tarrasque with enough prep-time like batman

 

 Tiamat doesn't need prep time, she can fly.  And has the ability to actually plan tactics beyond "hit it until it stops moving."

Also, the Primeval Dominance ability is just weird and makes it blatant that this was a monster made to fight other monsters: an ability that targets something that player characters don't get just sticks out poorly on the stat block.

Yes, some things that I don't like for dnd monsters are how they work in the world. All the monsters are designed to revolve around the party, so normally when I design monsters, i design them like how they would function in the world.

But the Tarrasque doesn't even need Primeval Dominance, with its pure ability to tank until Tiamat fails a CON save on its roar. Or Timat could just never approach it if that's what you're saying with the flying. Which, in case, yeah, the Tarrasque can't really go after her.

Quote from SentientSteel >>

That is fair, but don't people have general knowledge on how to make a good boss fight?

It's not as easy as you might think, but if you're going to create a variant, your goal should be 'better boss fight', not more powerful as such.

Hard to say because 2024 doesn't have stats for any godlike entities, besides the Colossals, Celestials etc.

Even  the Titan's Thunderous Bellow would not help the Tarrasque against Tiamat.  Flight gives her the ability to stay in it's read quarter away from the bellow and continue to hit it from behind.