Transmorpher Beacon

Transmorpher Beacon is available from the Blizzard Shop or the In-Game Store for $10 or €10. It was released on March 19, 2019. It summons an Ethereal Transmorpher who can reshape the player to have the appearance of a random dungeon or raid boss.

Description
Play Like a Boss! ''The ethereals have a twisted new trick up their sleeves, and they’re ready to traverse the nether to help you spread some chaos and confusion on the battlefield. Use this beacon to summon an Ethereal Transmorpher who can turn you and your allies into some of the most fearsome foes Azeroth has ever known.''
 * Blizzard Shop

Possible transformations
There are a total of 97 known appearances:

Notes and trivia

 * There is a random chance for an appearance to yell out a random line from their boss encounter.
 * The transformation effect persists through death.
 * 25% of every purchase will be contributed to the 2019 World of Warcraft Arena World Championship prize pool until October 15, 2019.