Searching for a reference.

[Empyreal Dragon]

In a discussion with a friend about the tarrasque. We're arguing about if more than one can exist.

I pulled up the planet falx from spelljammer as my argument that they can.


Is there a reference somewhere that specifically says only one tarrasque can exist in a universe?

[Asmotherion]

Nope; However it would be cruel as a DM to pull more than 1 before the PCs hit level 18.

Spelljamer ones are rather docile, and won't attack unprovocked, that's why they work.

[Khedrac]

If you read the original description of Falx more closely, they top predators have the same statistics of tarrasques not that they are tarrasques, therefore they don't break any one per planet rule.

[Silly Name]

Falx is specifically an anomaly. The MM entry of the Tarrasque always states that there is only one per Prime Material Plane/Planet.

Sure, theoretically there could be other planets like Falx... But more likely not.

[ShurikVch]

Not a 3.X, but still:

Halaster Blackcloak, the Mad Mage of Undermountain, always has a contingency in place. As long as Undermountain remains beneath the city of Waterdeep, Halaster can never truly die within its walls, for the dungeon rebuilds the mage’s body on the rare occasions when adventurers “kill” Halaster.

Halaster realized that if adventurers destroyed all of Undermountain (a nigh impossible feat more difficult than even slaying the mage), he would lose his immortality. To further protect his life, Halaster took some of the rooms and halls of Undermountain and flung them across the multiverse, including other worlds of the Material Plane. With Undermountain spread across existence, the task of permanently killing Halaster is even more difficult.

Unfortunately for the mage, a party adventurers recently killed him in his dungeon beneath the City of Splendors. When Halaster’s body reformed, he found himself in Falx, another world of the Material Plane inhabited entirely by enormous, carnivorous monsters with endless appetites. These scaly bipeds are closely related to the tarrasque, an infamous monstrosity feared across the worlds of the Material Plane. Halaster, now obsessed with punishing the adventurers who killed him, began to hatch a plot. If one tarrasque could level an entire city, what could a planet’s worth of the beings do to Faerûn?


https://pics.me.me/thumb_nvasion-tarrasques-from-the-planet-of-guild-an-epic-adventure-46654028.png

[Psyren]

Depends on the setting. Golarion has just one.

[QuickLyRaiNbow]

Specific > general. The MM says one, most settings either say nothing or have one, the Spelljammer metasetting has many. Clarifying whether you're talking about a world or a material plane would help, as would whether Spelljammer is in play as it's the only thing I know of that says specifically otherwise.