If you start to head to the giant tomb of storms head, then you will see 2 pillars with red markings on them by the shops. They are on a time, so if you wait around long enough, you will see the tips starting to glow, and the teleporter at thier base active (if your not lucky enough to go by there when its active), and the trainer is on the roof of that shop.
where is the buff minion trainer? I forgot.