Blizzard announced in a blue post that they have disabled the Mythic Keystone Vendor on the Shadowlands Beta. The Keystone Vendor previously gave players +10 keys to be able to test Mythic plus content and various affixes.
In order to get a keystone now on the Shadowlands Beta, players will have to play Necrotic Wake, Plaguefall, Mists of Tirna Scithe, or Halls of Atonement at Mythic difficulty and be granted a +2 key to start the Keystone grind from the beginning.
View Blue Post
Thank you everyone for your feedback on Mythic Keystone Dungeons so far! Your experiences have helped inform a number of improvements to both dungeons and affixes.
Starting with this week’s Beta update we have disabled the Keystone Vendor on the Torghast realm. Keystones can still be acquired though normal gameplay, and we will continue to review feedback and make adjustments as needed.