What it says on the tin. How to best use them, weaknessess that PC's can exploit and how to counter those weakneess. going off the current mnster manual sheet says:
DEFENCE
Has an AC of 25, which makes most attacks glance off of it. Unless they have weapons or spells and spell like abilities boosting them and hindering the enemy, most players would need a nat 20 to hit it.
It has Strength 30 (so +10 to physical abilities), A Dex of 11, Constitution of 30, Int of 3 (so -4 to inteligence base things) Wisdom of 11, and charisma of 11.
it does have a +9 saving throw bonus in the last three areas (+5 for inteligence due to how low it is) so it has a fair chance of still saving.
Its immune to Charmed, Frightened, Poison, Paralysis, fire, and any none magical bludgeoning, piercing, and slashing attacks.
A Proficiency bonus of 9, blind sight 120ft, passive perception 10.
3 Legendary resistances to auto save, Magic Resistance that gives it advantage on magical saves, and its reflective carapace has a 5/6 chance to ignore magic missile spell, a line spell, or any other spell that requires a ranged attack roll, and on that roll of 6 reflects it back at you.
Its a tough cooky, but that is just defense. Offence its a nightmare.
It moves 40ft, which is about as fast as most PCs on foot if not much faster.
It can make a Frightful Presence, a bite, 2 claw attacks, a horn attack, and a tail attack. Frightful presence means any creature of the big T's choice within 120ft must pass a DC17 Wisdom save or be frightened for a minute.
Its other attacks have +19 to hit, so depending on your AC it can roll a 2 and hit most creatures in the game. Bite and horns have a ten foot range, claws a 15foot, and tail 20ft. Claws deal 4d8+10 slashing damage, horns 4d10 Piercing, and the tail 4D10+10 bludgioning that if it hits then makes the target pass a Strength 20 save of be knocked prone.
The bite is worse as not only can it deal 4D12+10 piercing damage, it then grapples them (needs a Escape DC of 20). WHilee grappled the Tarasque can only bite them, but if the target is large or smaller they can be swallowed. If they are still grappled and they take another bite from the big guy, they take the bite damage and go down its throat. Good news, no longer grappled. Bad news you are now restrained, blinded, and in total cover against any attacks and effects outside of the Tarrasque. While the latter might be a good thing, you remember you have been eaten alive and now are entering its stomach and will take 16D6 acid damage on the start of the Tarrasques's turn so hope you are resistant to that. The only way out and still be alive is for the big guy to take 60 damage in a single turn, fail a DC 20 con save (which it has +10 to), and it regurgitates you. You lie prone within 10 feet of the big guy. Or it dies and you must spend 30ft of movement leaving it and going in a prone state.
And if its against a building or object, these attacks do double damage.
And being a legendary creature, it has 3 legendary actions that can be taken on the PC's turns. 1. Claw or Tail attack, 2. move up to half its speed.3 use up 2 slots and make a bite/use swallow.
and it has an HP of 33D20+330 (so between 363 and 990 Hp). You will earn that 155,000XP
So to fight it, you need some endgame gear and spells. Its immune to charm so no sleep spells, and its most range spells are out of the question, not completly. Ones that use a melee attack such as Mordenkainen's Sword, spiritual weapon, Thorn whip, or vampiric touch. You can try to see how well its +9 Wisdom is with Confusion might work, Dissonnt WHispers, eye bite, mind spike, reality break, staggering smite and more.
If you want to try to use Imprisonment, you could try holding its attention for 10 rounds.
It only has a +5 to Intelligence savs, so Psychic Scream, mind sliver, Synaptic Static, and Tasha's Mind Whip.
Dex saves something it has no bonues against, could include Acid Splash, Black Tentacles, Call Lightning, Disintegrate, Enervtion and more.
I know one strategy that I hear is to have a flying race (namley Arakocra) and have them shoot at it. The Tarrasques is a gargantuan creature so its tall, and I am assuming it can jump so why not make it jump and use its attacks with really good range? It backflipping to do a tail attack in the air is 30 feet, and if it hits it can force them to be knocked prone. A Prone flyer is falling that many feet to the ground. Crocodiles jump out of the water to get prey all the time, and they have an Intelligence of 2 in the game. This thing is literally double their brain power.
For something home brew, have it throw stuff. Its probably going to miss, BUTT its using building and debris as ammunition; if it misses, the DM can then say what it hit.
What are your thoughts on this, and will this guy make a comeback in the 5.5?
AC 25 is not that hard to hit for high level characters even without end game equipment. Weapon attacks do need to be magical but a Level 17 character will nearly always have +12 to hit even with a +1 weapon so will have a 40% chance to hit.
The Tarrasque has no defence against flying creatures. Sure it can jump but the height it can jump is limited. The tarrasque is 50ft tall and with a str modfier of +10 can jump 13ft (with a run up) the tail has a reach of 20 ft so even you say it can back flip without an acrobatics check the highest it can hit is 83ft. A creature flying at 90ft is perfectly safe from the tarrasque and is less than 40ft from the the top of the tarrasque so within range of most ranged weapons and spells (and they can go down 10 ft make an attack with 30 ft range and fly back up). You don't even need a flying race, at high levels flying is pretty easy. Paladins can have a flying mount, items like winged boots and flying brooms are uncommon, a sorcerer or wizard could upcast fly on the whole party (a warlock could cast it on 3 PCs which should be enough given other options) and many subclass features offer flight.
If I were running a tarrasque encounter, I’d look for ways to counter flying PCs. Which jegpeg sums up pretty nicely why flying is the tarrasque’s kryptonite.
Though a low magic (item) campaign could also help, as you force the casters to concentrate on Magic Weapon instead of fly.
Besides that, the first step is not to have the fight in a big open field. Have some trees there to give it cover from above, or put it in a cavern where the PCs can’t get altitude. Or, the better way, imo, is to have it attacking a town. There’s lots of civilians on the ground, fleeing for their lives. If the PCs won’t stand on the ground and fight it, the tarrasque will just destroy and/or kill whatever it can reach. So if the characters want to just stay airborne, they’ll be watching scores of innocents die while they’re safely out of range.
I agree with Xalthu, a Tarrasque in a giant field is not particularly scary. It's move speed it actually pretty slow for end-game and it's trapped on the ground meaning the PCs can set up all kinds of barriers to block it getting to them, or simply take to the air to avoid it.
The point of a Tarrasque is to have it destroying a city. It's a Kaiju-like monster, no one cares if it's out in the wilderness, it's only when it's knocking over sky scrapers and trampling busses that it's terrifying. You should absolutely have it attacking a major city with tons of innocent civilians (or better yet NPCs the party care about) right in its way. Also use the "Cleave through enemies" optional rule in the DMG to allow the Tarrasque to take out 3 or 4 commoners with a single tail swipe.
I'd also suggest writing HB rules for damage dealt by collapsing buildings, because the Tarrasque should be so big it often attacks the players / civilians by knocking a building on them rather than directly attacking them. Plus, don't limit yourself to a 4x4 token for the Tarrasque, Gargantuan is the biggest size category around which means it includes all monster bigger than Huge (also Forcecage can completely neuter the Tarrasque so make sure it is too big to fit inside).
Some day I'm going to start a campaign with a Tarrasque encounter in a large town. I'm going to tell my players ahead of time exactly what they'll be fighting at level 1 so they can build characters accordingly. It's a fairly well-worn meme at this point that a level-1 Owlin Warlock can fly 60 feet directly above the Tarrasque and wear it down with Mind Sliver over the course of something like forty-five minutes; that may be so, but the Tarrasque can do a lot of damage in 45 minutes. I wouldn't have the Tarrasque attack the PCs directly; in fact, I wouldn't have it so much as acknowledge their existence. Once they bring the monstrosity down (which I'm sure they'll do eventually), they'll instantly jump up to 8th level... but now what? The town is flattened. Hundreds of people are dead or missing. The city's defense infrastructure is devastated, and there's a 50-foot-tall, 70-foot-wide, magic-reflecting body lying in a pile of rubble in the center of town.
The party will no doubt be hailed as heroes; how will they help or hinder the town's recovery? Will they keep the survivors safe from those who would predate on the Tarrasque-fall, or will they be the ones who exploit the corpse for their own gain? Will they search for answers about the source of the attack? Are there answers to find?
I think this is the most interesting way to use the Tarrasque; not so much as an engaging combat encounter (which it isn't) but as an event that kicks off or changes the course of a campaign.
Another approach is to make it a race against time. The Tarrasque is attacking something that if it breaks through something terrile will happen (e.g. a portal to an evil plane will be revealed or some mad demi-god will be released, somewhat like the chained oblivion in Critical Role 2). The party can either use all their biggest resources to destroy the tarrasque as quickly as possible or hold things back so they have something left to fight the greater enemy if they fail to defeat the tarrasque in time.
I always think it's amusing when people say things like "90ft and you're save from the tarrasque" - no you're not. Those big clawed arms can throw shit. If you get its attention, it might as well grab the next bulder/building/whatever and throw it at you. Stat blocks are not exclusionary.
My advice for DMs would be: Never FIGHT a Tarrasque, that's not what it's for. At least not in a way that doesn't involve a bunch of sessions to prepare/find help/find some kind of powerfull stuff to help fight it.
If your players cheese the Tarrasque, you did it wrong.
I always think it's amusing when people say things like "90ft and you're save from the tarrasque" - no you're not. Those big clawed arms can throw shit. If you get its attention, it might as well grab the next bulder/building/whatever and throw it at you. Stat blocks are not exclusionary.
My advice for DMs would be: Never FIGHT a Tarrasque, that's not what it's for. At least not in a way that doesn't involve a bunch of sessions to prepare/find help/find some kind of powerfull stuff to help fight it.
If your players cheese the Tarrasque, you did it wrong.
I think that's a perfectly valid interpretation, but I want to push back gently. We don't know that the Tarrasque can throw things just because it's very strong. There's two reasons I don't think we can assume this.
Watsonian explanation: Throwing objects accurately is a fairly rare ability in our world; humans and closely related primates are basically the only animals that can do it. I wouldn't expect a giant reptile, even a very strong one, to be able to make use of thrown projectiles.
Doylist explanation: While stat blocks are not exclusionary, generally speaking a stat block should contain all the information necessary to run a monster at its intended challenge rating. That is why players pay for stat blocks, after all. I don't think we should make DMs feel bad for picking up a monster they paid for and expecting it to work as written. If you have to homebrew a monster to make it good (and adding throw attacks to the Tarrasque is homebrew, unless you're using the standard 1d4 for improvised weapons), that's a badly designed monster.
While I would be able to go with both your explanations (and while we're at it, thanks for the words "watsonian" and "doylist" - those are two really helpful words I learned now), some comments back:
About your watsonian explanation: I guess that could be a problem (especially since there is art of the Tarrasque with different arms etc.) - but I think you could argue when throwing a big enough thing you don't have to aim as accurate anymore.
About your doylist explanation: Yes - and no. While that is true for normal statblocks and monsters, I'd argue for "boss type" monsters and statblock there should be a bit of tweaking allowed, especially when players try some "tricking the game" out of character. Same thing: Rules as written: If you throw down a 10 by 10 ft aquare of ball bearings and the terrasque walks over it with its gargantuan size - it still needs to do a dex save and with its +0 in dex has quite a good chance at failing that one. Should a DM allow that to happen? - probably not, a few ball bearings are quite unlikely to stop something THAT huge. But it would be in the rules.
All good notes. I had completly forgotten about the proficiency.
What page is the building damage on?
As far as I know there aren't official rules for building damage, I would look at the "Traps" section of the DMG, and use those. Use the size/construction material of the building as the "Deadliness" of the trap - a 2-story stone temple with a spire falling on you is going to hurt a lot more than a one-story mud & thatch hut. Then use a Dex save vs half damage over an appropriate area.
You can look at the "Objects" section of the DMG to determine how easy / hard it is for the Tarasque to collapse any particular building.
I was once in a wilderness campaign where the party was 2 Ranger Gloom Stalkers , 2 Ranger Hunters, 2 druids with call lightening. Each was level 15. The Rangers were all Archers. We were a group that would infiltrate the enemy war camps and cause havoc. The DM made a huge mistake having the Tarrasque attack a small village on the open plains. The Rangers all had Sharp Shooter. The poor Tarrasque never got close to us.
It was honestly a waist of a legenday monster since the battle was in a wide open area where we could just hit and move. I will say my oth Bow was so very pleased with me!
Use them the same way you would use any natural disaster.
A tarrasque has emerged just outside the city and is now tearing its way through the walls!
The PCs' goal is to minimise the damage to the city. If the PCs fly up and plink the monster with arrows then it will just ignore them and continue tearing through buildings, and the mayor will yell at the PCs for not stopping the destruction. To stop the monster attacking buildings, they need to give it a more attractive target. The barbarian, perhaps…
I'm vaguely offended by the idea of tarrasques - plural. It's a 'great reptilian punisher sent by the gods to end the world'. Somewhat incompetent gods, one must conclude, and maybe they should have sent more than one. But they didn't! =)
Anyways, personally I'd use the tarrasque in much the same way as I'd use a particularly dangerous terrain feature. Like, you can go to mount doom if you want to, but it's like ... Mt. Doom. It's in the name, sorta, that you might not want to. I'd do kinda similar with the tarrasque: Have it wander around aimlessly - well-informed guides know it's approximate whereabouts, and steer caravans and travellers well clear. Then, sometimes, maybe it wanders closer to inhabited lands, and adventurers push or lure it away again.
I would not, however, tie it to any plot. It's dumb. Like, literally Int 3. So while it can certainly be monstrous, it cannot really carry much of a plot. Well, not on it's own. But maybe a quest could be: The tarrasque is about to eat Innocentville. Buy a herd of cows, and use those to gently (well, not for the cows) steer it away towards the mountains, where it becomes an orc problem, not an us problem. That's still a fairly dumb quest, but also somewhat humorous. Also, since no plan ever survives first contact with the tarrasque, further hilarity may ensue.
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Blanket disclaimer: I only ever state opinion. But I can sound terribly dogmatic - so if you feel I'm trying to tell you what to think, I'm really not, I swear. I'm telling you what I think, that's all.
It could be a plot point item. Something a big bad is trying to awaken, or a prophesied doom. The imprisonment spell can break understating circumstances, so have it break out of the gem when it does.
Depending on how well players do in a campaign I am working on, it might be a 4 way brawl in the middle of a big city between this, Yeenagu, a Pitfind, and an Elder Black Dragon with spells. Godzilla music will be playing.
The one time my group ever used the tarrasque, I ran a three-shot in which a mysterious puzzle-box was thrust upon them--pursued by a cult of some kind. The secret turned out to be not the contents, but the box itself, which would serve as a kind of map to the location of an "ancient weapon". In true Indiana Jones fashion, the cult got the box back and the party raced off to catch them in the act of digging up the long-buried and very irritated tarrasque.
Despite being rather high-level, the party opted after a few rounds of nonsense to just re-bury the thing using a bunch of summoned earth elementals, since it had already eaten half the cultists... and the arm of their most powerful druid.
I'm DMing a group of friends through Icewind Dale: Rime of the Frostmaiden and they are about to get to the part where they'll find a "Scroll of Tarrasque Summoning", I canNOT wait until that temptation and debate amongst the group unfolds. Tentowns beware!
Stay away from it until the Diviner can Portent a low die (and a high die alongside it wiould be ideal).
Give an Open Hand Monk slippers that double movement.
Have the Open Hand monk start max distance away from the big T. They will have a very good chance to overcome Frightful Presence. Then, they run in and Dim Mak the creature. Use the Portent to ensure the beastie dies.
Reward the players with a suitably graphic description of the big T exploding.
What it says on the tin. How to best use them, weaknessess that PC's can exploit and how to counter those weakneess. going off the current mnster manual sheet says:
DEFENCE
Has an AC of 25, which makes most attacks glance off of it. Unless they have weapons or spells and spell like abilities boosting them and hindering the enemy, most players would need a nat 20 to hit it.
It has Strength 30 (so +10 to physical abilities), A Dex of 11, Constitution of 30, Int of 3 (so -4 to inteligence base things) Wisdom of 11, and charisma of 11.
it does have a +9 saving throw bonus in the last three areas (+5 for inteligence due to how low it is) so it has a fair chance of still saving.
Its immune to Charmed, Frightened, Poison, Paralysis, fire, and any none magical bludgeoning, piercing, and slashing attacks.
A Proficiency bonus of 9, blind sight 120ft, passive perception 10.
3 Legendary resistances to auto save, Magic Resistance that gives it advantage on magical saves, and its reflective carapace has a 5/6 chance to ignore magic missile spell, a line spell, or any other spell that requires a ranged attack roll, and on that roll of 6 reflects it back at you.
Its a tough cooky, but that is just defense. Offence its a nightmare.
It moves 40ft, which is about as fast as most PCs on foot if not much faster.
It can make a Frightful Presence, a bite, 2 claw attacks, a horn attack, and a tail attack. Frightful presence means any creature of the big T's choice within 120ft must pass a DC17 Wisdom save or be frightened for a minute.
Its other attacks have +19 to hit, so depending on your AC it can roll a 2 and hit most creatures in the game. Bite and horns have a ten foot range, claws a 15foot, and tail 20ft. Claws deal 4d8+10 slashing damage, horns 4d10 Piercing, and the tail 4D10+10 bludgioning that if it hits then makes the target pass a Strength 20 save of be knocked prone.
The bite is worse as not only can it deal 4D12+10 piercing damage, it then grapples them (needs a Escape DC of 20). WHilee grappled the Tarasque can only bite them, but if the target is large or smaller they can be swallowed. If they are still grappled and they take another bite from the big guy, they take the bite damage and go down its throat. Good news, no longer grappled. Bad news you are now restrained, blinded, and in total cover against any attacks and effects outside of the Tarrasque. While the latter might be a good thing, you remember you have been eaten alive and now are entering its stomach and will take 16D6 acid damage on the start of the Tarrasques's turn so hope you are resistant to that. The only way out and still be alive is for the big guy to take 60 damage in a single turn, fail a DC 20 con save (which it has +10 to), and it regurgitates you. You lie prone within 10 feet of the big guy. Or it dies and you must spend 30ft of movement leaving it and going in a prone state.
And if its against a building or object, these attacks do double damage.
And being a legendary creature, it has 3 legendary actions that can be taken on the PC's turns. 1. Claw or Tail attack, 2. move up to half its speed.3 use up 2 slots and make a bite/use swallow.
and it has an HP of 33D20+330 (so between 363 and 990 Hp). You will earn that 155,000XP
So to fight it, you need some endgame gear and spells. Its immune to charm so no sleep spells, and its most range spells are out of the question, not completly. Ones that use a melee attack such as Mordenkainen's Sword, spiritual weapon, Thorn whip, or vampiric touch. You can try to see how well its +9 Wisdom is with Confusion might work, Dissonnt WHispers, eye bite, mind spike, reality break, staggering smite and more.
If you want to try to use Imprisonment, you could try holding its attention for 10 rounds.
It only has a +5 to Intelligence savs, so Psychic Scream, mind sliver, Synaptic Static, and Tasha's Mind Whip.
Dex saves something it has no bonues against, could include Acid Splash, Black Tentacles, Call Lightning, Disintegrate, Enervtion and more.
I know one strategy that I hear is to have a flying race (namley Arakocra) and have them shoot at it. The Tarrasques is a gargantuan creature so its tall, and I am assuming it can jump so why not make it jump and use its attacks with really good range? It backflipping to do a tail attack in the air is 30 feet, and if it hits it can force them to be knocked prone. A Prone flyer is falling that many feet to the ground. Crocodiles jump out of the water to get prey all the time, and they have an Intelligence of 2 in the game. This thing is literally double their brain power.
For something home brew, have it throw stuff. Its probably going to miss, BUTT its using building and debris as ammunition; if it misses, the DM can then say what it hit.
What are your thoughts on this, and will this guy make a comeback in the 5.5?
A couple of things:
AC 25 is not that hard to hit for high level characters even without end game equipment. Weapon attacks do need to be magical but a Level 17 character will nearly always have +12 to hit even with a +1 weapon so will have a 40% chance to hit.
The Tarrasque has no defence against flying creatures. Sure it can jump but the height it can jump is limited. The tarrasque is 50ft tall and with a str modfier of +10 can jump 13ft (with a run up) the tail has a reach of 20 ft so even you say it can back flip without an acrobatics check the highest it can hit is 83ft. A creature flying at 90ft is perfectly safe from the tarrasque and is less than 40ft from the the top of the tarrasque so within range of most ranged weapons and spells (and they can go down 10 ft make an attack with 30 ft range and fly back up). You don't even need a flying race, at high levels flying is pretty easy. Paladins can have a flying mount, items like winged boots and flying brooms are uncommon, a sorcerer or wizard could upcast fly on the whole party (a warlock could cast it on 3 PCs which should be enough given other options) and many subclass features offer flight.
If I were running a tarrasque encounter, I’d look for ways to counter flying PCs. Which jegpeg sums up pretty nicely why flying is the tarrasque’s kryptonite.
Though a low magic (item) campaign could also help, as you force the casters to concentrate on Magic Weapon instead of fly.
Besides that, the first step is not to have the fight in a big open field. Have some trees there to give it cover from above, or put it in a cavern where the PCs can’t get altitude.
Or, the better way, imo, is to have it attacking a town. There’s lots of civilians on the ground, fleeing for their lives. If the PCs won’t stand on the ground and fight it, the tarrasque will just destroy and/or kill whatever it can reach. So if the characters want to just stay airborne, they’ll be watching scores of innocents die while they’re safely out of range.
I agree with Xalthu, a Tarrasque in a giant field is not particularly scary. It's move speed it actually pretty slow for end-game and it's trapped on the ground meaning the PCs can set up all kinds of barriers to block it getting to them, or simply take to the air to avoid it.
The point of a Tarrasque is to have it destroying a city. It's a Kaiju-like monster, no one cares if it's out in the wilderness, it's only when it's knocking over sky scrapers and trampling busses that it's terrifying. You should absolutely have it attacking a major city with tons of innocent civilians (or better yet NPCs the party care about) right in its way. Also use the "Cleave through enemies" optional rule in the DMG to allow the Tarrasque to take out 3 or 4 commoners with a single tail swipe.
I'd also suggest writing HB rules for damage dealt by collapsing buildings, because the Tarrasque should be so big it often attacks the players / civilians by knocking a building on them rather than directly attacking them. Plus, don't limit yourself to a 4x4 token for the Tarrasque, Gargantuan is the biggest size category around which means it includes all monster bigger than Huge (also Forcecage can completely neuter the Tarrasque so make sure it is too big to fit inside).
Some day I'm going to start a campaign with a Tarrasque encounter in a large town. I'm going to tell my players ahead of time exactly what they'll be fighting at level 1 so they can build characters accordingly. It's a fairly well-worn meme at this point that a level-1 Owlin Warlock can fly 60 feet directly above the Tarrasque and wear it down with Mind Sliver over the course of something like forty-five minutes; that may be so, but the Tarrasque can do a lot of damage in 45 minutes. I wouldn't have the Tarrasque attack the PCs directly; in fact, I wouldn't have it so much as acknowledge their existence. Once they bring the monstrosity down (which I'm sure they'll do eventually), they'll instantly jump up to 8th level... but now what? The town is flattened. Hundreds of people are dead or missing. The city's defense infrastructure is devastated, and there's a 50-foot-tall, 70-foot-wide, magic-reflecting body lying in a pile of rubble in the center of town.
The party will no doubt be hailed as heroes; how will they help or hinder the town's recovery? Will they keep the survivors safe from those who would predate on the Tarrasque-fall, or will they be the ones who exploit the corpse for their own gain? Will they search for answers about the source of the attack? Are there answers to find?
I think this is the most interesting way to use the Tarrasque; not so much as an engaging combat encounter (which it isn't) but as an event that kicks off or changes the course of a campaign.
Another approach is to make it a race against time. The Tarrasque is attacking something that if it breaks through something terrile will happen (e.g. a portal to an evil plane will be revealed or some mad demi-god will be released, somewhat like the chained oblivion in Critical Role 2). The party can either use all their biggest resources to destroy the tarrasque as quickly as possible or hold things back so they have something left to fight the greater enemy if they fail to defeat the tarrasque in time.
I still want to run an adventure in which the party is inside the beast. They just don't know it.
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All good notes. I had completly forgotten about the proficiency.
What page is the building damage on?
I always think it's amusing when people say things like "90ft and you're save from the tarrasque" - no you're not. Those big clawed arms can throw shit. If you get its attention, it might as well grab the next bulder/building/whatever and throw it at you. Stat blocks are not exclusionary.
My advice for DMs would be: Never FIGHT a Tarrasque, that's not what it's for. At least not in a way that doesn't involve a bunch of sessions to prepare/find help/find some kind of powerfull stuff to help fight it.
If your players cheese the Tarrasque, you did it wrong.
I think that's a perfectly valid interpretation, but I want to push back gently. We don't know that the Tarrasque can throw things just because it's very strong. There's two reasons I don't think we can assume this.
Watsonian explanation: Throwing objects accurately is a fairly rare ability in our world; humans and closely related primates are basically the only animals that can do it. I wouldn't expect a giant reptile, even a very strong one, to be able to make use of thrown projectiles.
Doylist explanation: While stat blocks are not exclusionary, generally speaking a stat block should contain all the information necessary to run a monster at its intended challenge rating. That is why players pay for stat blocks, after all. I don't think we should make DMs feel bad for picking up a monster they paid for and expecting it to work as written. If you have to homebrew a monster to make it good (and adding throw attacks to the Tarrasque is homebrew, unless you're using the standard 1d4 for improvised weapons), that's a badly designed monster.
While I would be able to go with both your explanations (and while we're at it, thanks for the words "watsonian" and "doylist" - those are two really helpful words I learned now), some comments back:
About your watsonian explanation: I guess that could be a problem (especially since there is art of the Tarrasque with different arms etc.) - but I think you could argue when throwing a big enough thing you don't have to aim as accurate anymore.
About your doylist explanation: Yes - and no. While that is true for normal statblocks and monsters, I'd argue for "boss type" monsters and statblock there should be a bit of tweaking allowed, especially when players try some "tricking the game" out of character. Same thing: Rules as written: If you throw down a 10 by 10 ft aquare of ball bearings and the terrasque walks over it with its gargantuan size - it still needs to do a dex save and with its +0 in dex has quite a good chance at failing that one. Should a DM allow that to happen? - probably not, a few ball bearings are quite unlikely to stop something THAT huge. But it would be in the rules.
As far as I know there aren't official rules for building damage, I would look at the "Traps" section of the DMG, and use those. Use the size/construction material of the building as the "Deadliness" of the trap - a 2-story stone temple with a spire falling on you is going to hurt a lot more than a one-story mud & thatch hut. Then use a Dex save vs half damage over an appropriate area.
You can look at the "Objects" section of the DMG to determine how easy / hard it is for the Tarasque to collapse any particular building.
I was once in a wilderness campaign where the party was 2 Ranger Gloom Stalkers , 2 Ranger Hunters, 2 druids with call lightening. Each was level 15. The Rangers were all Archers. We were a group that would infiltrate the enemy war camps and cause havoc. The DM made a huge mistake having the Tarrasque attack a small village on the open plains. The Rangers all had Sharp Shooter. The poor Tarrasque never got close to us.
It was honestly a waist of a legenday monster since the battle was in a wide open area where we could just hit and move. I will say my oth Bow was so very pleased with me!
Use them the same way you would use any natural disaster.
A tarrasque has emerged just outside the city and is now tearing its way through the walls!
The PCs' goal is to minimise the damage to the city. If the PCs fly up and plink the monster with arrows then it will just ignore them and continue tearing through buildings, and the mayor will yell at the PCs for not stopping the destruction. To stop the monster attacking buildings, they need to give it a more attractive target. The barbarian, perhaps…
I'm vaguely offended by the idea of tarrasques - plural. It's a 'great reptilian punisher sent by the gods to end the world'. Somewhat incompetent gods, one must conclude, and maybe they should have sent more than one. But they didn't! =)
Anyways, personally I'd use the tarrasque in much the same way as I'd use a particularly dangerous terrain feature. Like, you can go to mount doom if you want to, but it's like ... Mt. Doom. It's in the name, sorta, that you might not want to. I'd do kinda similar with the tarrasque: Have it wander around aimlessly - well-informed guides know it's approximate whereabouts, and steer caravans and travellers well clear. Then, sometimes, maybe it wanders closer to inhabited lands, and adventurers push or lure it away again.
I would not, however, tie it to any plot. It's dumb. Like, literally Int 3. So while it can certainly be monstrous, it cannot really carry much of a plot. Well, not on it's own. But maybe a quest could be: The tarrasque is about to eat Innocentville. Buy a herd of cows, and use those to gently (well, not for the cows) steer it away towards the mountains, where it becomes an orc problem, not an us problem. That's still a fairly dumb quest, but also somewhat humorous. Also, since no plan ever survives first contact with the tarrasque, further hilarity may ensue.
Blanket disclaimer: I only ever state opinion. But I can sound terribly dogmatic - so if you feel I'm trying to tell you what to think, I'm really not, I swear. I'm telling you what I think, that's all.
It could be a plot point item. Something a big bad is trying to awaken, or a prophesied doom. The imprisonment spell can break understating circumstances, so have it break out of the gem when it does.
Depending on how well players do in a campaign I am working on, it might be a 4 way brawl in the middle of a big city between this, Yeenagu, a Pitfind, and an Elder Black Dragon with spells. Godzilla music will be playing.
The one time my group ever used the tarrasque, I ran a three-shot in which a mysterious puzzle-box was thrust upon them--pursued by a cult of some kind. The secret turned out to be not the contents, but the box itself, which would serve as a kind of map to the location of an "ancient weapon". In true Indiana Jones fashion, the cult got the box back and the party raced off to catch them in the act of digging up the long-buried and very irritated tarrasque.
Despite being rather high-level, the party opted after a few rounds of nonsense to just re-bury the thing using a bunch of summoned earth elementals, since it had already eaten half the cultists... and the arm of their most powerful druid.
I'm DMing a group of friends through Icewind Dale: Rime of the Frostmaiden and they are about to get to the part where they'll find a "Scroll of Tarrasque Summoning", I canNOT wait until that temptation and debate amongst the group unfolds. Tentowns beware!
Stay away from it until the Diviner can Portent a low die (and a high die alongside it wiould be ideal).
Give an Open Hand Monk slippers that double movement.
Have the Open Hand monk start max distance away from the big T. They will have a very good chance to overcome Frightful Presence. Then, they run in and Dim Mak the creature. Use the Portent to ensure the beastie dies.
Reward the players with a suitably graphic description of the big T exploding.
NOTE: This won’t work with the new rules.
I assume "Dim Mak" is "Quivering Palm"; if so doesn't work- Legendary Resistances trump Portent.