Although we're still in the middle of the reveal season, it appears that Blizzard just leaked via mail part of the patch notes' content that will be shared tomorrow. Thanks u/Fakumon115 for the scoop!

Here is some of the leaked information:

  • Battlegrounds update
    • Diablo will return to Battlegrounds for a week.
    • New Hero (Ozumat) and new minion (Bubbler) available.
  • Mercenaries update
    • Y'shaarj Event consisting of 10 tasks (7-21 June).
    • New Mercenaries, including Y'shaarj (Legendary Protector) and Queen Azshara (Legendary Caster).
    • New zones and bounties.
    • Mystery Node reworked.
  • Solo content
    • Book of Heroes: Faelin

Quote From Reddit

BATTLEGROUDS UPDATES
  • Diablo returns Battlegrounds for just a week, starting from June 1st, to celebrate the launch of Diablo Immortal.
  • New Hero (Ozumat) and minion (Bubbler) available.
MERCENARIES UPDATES
  • New limited time event: Y'shaarj (7-21 June).
  • Completing all 10 tasks will grant you the Y'shaarj Mercenary, a Y'shaarj golden portrait, the Y'shaarj Diamond portrait and a total of 750 Mercenary coins.
  • You best allies against Y'shaarj for this event will be Humans and Pirates.
  • New Mercenaries, including Y'shaarj (Legendary Protector) and Queen Azshara (Legendary Caster).
  • New zones and bounties.
  • The Mysterious Nodes appearing on maps now give you the chance to find either a Cursed Treasure - which will hinder your characters for the rest of the turn - or Reward Bonuses that will add up to the ones you'll receive at the end of the bounty!
BOOK OF HEROES: FAELIN

When he finally has the chance to visit Zin-Azshari, Ambassador Faelin can't wait to face the dangers he could run into with his intrepid crew. But is the distant past just like he remembers it, or has something darker remained beneath the surface all this time?

This adventure can be played as three different characters. Completing all 17 tasks for the first time will reward you the Ghost Ship card back; completing all 17 tasks with a different character will reward you a Standard pack; completing all 17 tasks also with the third character will reward you a Voyage to the Sunken City card pack.