Excluse me, this is just the sort of exclusive exclusivity that makes enworld (i.e. exclusive news world) my destination for d&d-related exclusives.
That's not a monster, that's a force of nature. If I understand the Challenge system correctly, and I'm not saying I do, you'd need a group of 7-10 level 20 adventurers to stand a chance against the Challenge 30 Tarrasque and, even then, it'd be a challenging, even deadly fight. Yikes.
I have to wonder about the Tarrasque vs. Ancient Red Dragon. If your character sees this going down, Start running and hope you can run fast enough to get out of range.