Originally posted by sarteck:

Originally posted by Yakumo_2020:

Actually the Ground Shaking RAID unlocks when you kill a Troll and can continue to happen at any point from then on. I've killed every boss so far and I still get Trolls.

The Troll raid has two requirements for it to unlock; killing a troll, and killing the elder.

If you never kill the Elder, you never get troll raids.

Thanks for the correction, I had forgotten about the Elder part of the trigger. will edit my original comment.