Originally posted by vonVile:

It's always the same. Trolls. Trolls. Trolls.

Where is the damn variety?!

The more you play the game, and the farther you progress, the more types of raids unlock and get added to the collective pool of possible raids the game can select during it's scheduled check (when it checks to see IF a raid is about to happen and WHAT raid it will be).

Yeah what ^^^ he said... Check the wiki