The new Dual Talent Specialization Trainer added in Phase 3 of Season of Discovery known as «Grendag» can be found in Ironforge and Orgrimmar. For 50 gold, you can learn a dual talent specialization, a feature often requested in WoW Classic!
Grendag Brightbeard can be found in Ironforge and Orgrimmar.
Players on Season of Discovery are reporting that purchasing the dual talent specialization (50 gold) from Grendag Brightbeard while in combat will result in losing the 50 gold, but not learning dual talent! If you are interested in buying this, be sure you aren't in combat or doing PvP!
When Blizzard updates players on the issue or fixes it, we will update this post with the latest information.
Edit: Blizzard has removed the Grendag from the game.
Edit: Blizzard shared a Blue Post explaining that Grendag was removed.
Edit: Blizzard shared on Twitter that Grendag will return tomorrow in a different location.
Edit: In the Patch Notes for Phase 3, Blizzard states Grendag will be in Ironforge and Orgrimmar.
Edit: Blizzard has enabled Grendag Brightbeard ahead of schedule, he can now be found in Orgrimmar and Ironforge.