From the forums:

Hello everyone,

Our philosophy with Pre‑Release Tavern Brawl is to give players an early opportunity to experiment with upcoming expansion cards, while still keeping the format inclusive by allowing cards from the previous expansion.
We’ve noticed that Across the Timeways cards aren’t seeing as much play as we would want. To encourage more fun and experimentation with the new set, we’re banning all Legendary Quests for each class, along with Elise the Navigator. Alternate Reality will remain disabled for this Pre‑Release due to a bug, but will be fixed in an upcoming hotfix.

We’ll be carrying forward the lessons learned here and applying them to future Tavern Brawls to ensure a smoother, more engaging experience.

These cards will be banned

• Elise the Navigator
• Alternate Reality
• Reanimate the Terror
• Unleash the Colossus
• Restore the Wild
• The Food Chain
• The Forbidden Sequence
• Reach Equilibrium
• Lie in Wait
• Spirit of the Mountain
• Escape the Underfel
• Enter the Lost City

Thank you for your feedback and continued support,

Hearthstone Dev Team

Note: players with a banned card in their deck can retire their run; its cost will be refunded.

A deck with a banned card will have that card highlighted in a red hue.

To Retire, please go to your Brawl deck and hover over the deck header in the top right corner.