Monsters deck :
The 13 normal monsters are the same (goblin, skeleton, orc, vampire...) in WttD or WBttD, but the card back and illustrations are different, so if you want to play with the special monsters from WBttD, you need to use the WBttD's monsters cards.
=> One monsters deck from WttD OR WBttD (they are never shuffle together).
You can use all 8 adventurers.
Player aids :
Each player can have 3 player aids : the WttD one and the two from WBttD, so you can see which tile interact with which monster.
Thanks, I would have be so nice if this information had been in the rules.