How did the dancestor trolls die, and what do we know about pre-damage Mituna?

We know that Mituna had visions of bad stuff and tried to warn people about it and change it to protect his friends. We also know Kurloz was his Moirail, and probably the only personw ho knows what happened to him.

Also, Meenah blew them all up with the mini-Tumor in their Battlefield.