Q: I was reading about the tarrasque and a question came up. What would happen if a tarrasque meets another tarrasque?
A: To quote a wise man (we presume), in a battle no one can win… who wins? Essentially, this is what’s being asked. The 1st edition Monster Manual II listed the tarrasque’s Frequency as Unique, meaning there can be only one. Although Frequency is no longer part of the current monster stat blocks, the 3.5 edition tarrasque explicitly states, “The legendary Tarrasque -- fortunately, only one exists -- is possibly the most dreaded monster of all (except for the largest dragons).
So what would happen if a tarrasque meets a tarrasque coming through the rye? Fortunately we need not contemplate such a world…