The Hearthstone Battlegrounds team has announced a ladder refresh and a huge update on August 31 that will add two new heroes into the tavern: a Pandaren NPC named Master Nguyen, and a Hearthstone original character called Cariel Roame. The update will also add the new keyword Avenge.
In terms of random, Master Nguyen might be the highest variance hero ever seen in the tavern, since his passive Hero Power, Power of the Storm, offers you two random other Hero Powers to choose from at the start of every turn. Due to it being passive, it will also automatically trigger every turn, meaning that you can’t choose to hold onto any Hero Power you get, as it will be forcibly replaced with a new choice the next turn.
Cariel Roame’s Hero Power: Conviction (Rank 1) costs one gold and gives one random friendly minion +1/+1, but will upgrade at Tavern Tier 3 into Conviction (Rank 2) giving three random friendly minions +1/+1 and then upgrades a final time at Tavern Tier 5 into Conviction (Rank 3) which will give five random friendly minions +1/+1. Anyone who plays the Hearthstone VCG will recognize that her Hero Power pays homage to the card Conviction, which levels up in rank once you hit both five and ten mana.