Complete Today’s Pet Rescue (even if you already have it at Mythic ascension)
Then complete another match or restart the game.
To see the Brand New Arena Event Tracker.
I know the devs have full time jobs so they couldn’t bother with making more than this…
Big of an announcement about a brand new event.
But to be fair to them. Given the mechanics and the “rewards”…I wouldn’t be motivated to make a big deal out of it either.