Do I have to watch all of the related tv shows before watching Reunion? And what is the order to watch all of them?
1. To answer the first question, you don't have to watch them to understand Reunion. Wu Xie, Pangzi, and Qiling will be well-established friends, but the show does try to cover the basics for new fans. Also, the overarching storyline does not involve the other tv shows.
2. If you want to understand the characters better and want to know the order to watch all the related series, then here is the chronological order of the shows:
- Mystic Nine (optional): this is a stand-alone prequel (does not include Wu Xie, Qiling, or Pangzi) but involves the nine major grave robbing families in Changsha (includes Wu Xie's family (The Wus)). It helps to watch this because it involves the family politics that is mentioned throughout the shows.
- The Lost Tomb: the start of Wu Xie's tomb raiding adventures
- The Lost Tomb 2: Wu Xie starts a new adventure in an undersea tomb
- The Lost Tomb 2: Explore with the Note: Wu Xie continues his adventure on Changbai Mountains.
- Ultimate Note: Follows Ultimate Note. Wu Xie starts to unravel all of the conspiracies.
A large gap of time in the Lost Tomb world (like 10yrs from Lost Tomb 2). Hence why Wu Xie looks older.
- Tomb of the Sea: After all these years, Wu Xie is hardened by all of the conspiracies and is different from his innocent self in The Lost Tomb.
- Reunion: Sound of the Providence: Here you are. Have fun!
- Reunion: Sound of the Providence 2: Second season of Reunion.
Cleaner version here.
If you want more information, there is a fandom wiki of the books the shows are based on here and the show wiki here (both have spoilers!) If you have any more questions, feel free to ask~