[Spoilers] Calamity: a question about Ildithia

Spoilers below!

Okay, I just finished Calamity and I was thinking about the parallel universe in which Firefight lives in. Ildithia (the city of salt that travels around) seems to have some bad ramifications in the world in which the Reckoners takes place, but in Firefights world it is still seems to be allowed to roam unchecked even though most of the Epics didn't go bad there. Just got me wondering why it would be allowed to continue existing, or why in a world with Hero Epics it was created at all. Maybe it has benifits that I just missed. Any ideas would be appreciated. I know it is not a question of great importance, but it was just one of those weird questions that stuck with me.