WoWDB

Source (emph. mine): World of Warcraft Pet and Heroes of the Storm Mount Rewards

World of Warcraft is teaming up with Heroes of the Storm to celebrate the launch of Blizzard’s new free-to-play team brawler with an epic Grave Golem pet—summoned into Azeroth straight from Heroes’ Haunted Mines map! Beginning June 2, anyone who reaches Player Level 20 (ed. note: player profile, not individual hero character level) in Heroes of the Storm will be awarded a Grave Golem in World of Warcraft. To unlock this accursedly endearing creature once you’ve reached your goal, simply log in to World of Warcraft after Heroes launches on June 2 and claim your reward.

That’s not all: if you reach level 100 with any character in World of Warcraft, you’ll earn an Ironside Dire Wolf mount to use in Heroes of the Storm—an epic ride to represent your legendary accomplishments on Azeroth and Draenor.

Both rewards will be available starting June 2, 2015, after Heroes of the Storm officially launches. If you’ve already reached Player Level 20 in Heroes of the Storm or level 100 in World of Warcraft, you will receive these rewards shortly after the release of Heroes of the Storm.

We’ve also got some awesome rewards in store for our Hearthstone friends—check here to find out how to earn them.