Impressive. I like that 500d6 damage crater.
Although, I think the crater would be much wider than it was deep, unless I read that wrong. Could make it go in 3d20 with a radius of 3x it's distance down, or something like that. Craters don't seem to be hemispherical.
...This seems like a perfect replacement for the tarrasque, or the 'rocks fall, everyone dies.' ..."Giant extra-terrestrial golem falls, everyone dies"?