Somehow the mod crashed the game
https://pastebin.com/zTpUERcN

AlexModGuy/Ice_and_Fire#1755 (comment)

OKAY I had this same crash log. All I had to do was disable Myrmex from generating/spawning in the world, so effectively removing them from the game.

Of course this means you need to start a new world in order for this fix to be effective. Unless you want to use a world/chunk editor to remove them from your current world if you so desired.

Ye but if removing content is the solution to solve a bug it’s not solved at all XD

Oh for sure. It's still an issue that the devs of one of these two mods needs to solve. But my suggestion still serves as a temporary workaround until then