correct me if im wrong,
1 - you've got to raid a gym that has (ex raid) status tagged(any kind of raid, 1 star - 5 star). Can see it on the top left on that gym. Once, your raid is succesful, after awhile, you'll get an invite.

2 - those who got the pass for the ex raid(succesful raid), can invite their ultra friends(those who didn't raid that particular gym) to the raid as well.

This post has been edited by jojo_g2: Dec 18 2018, 09:34 AM