The Barbarian assault ticket is an item that is obtained from Captain Cain or Commander Connad by requesting to change your current wave in Barbarian Assault back to wave one (only if your current wave is higher than one), or attempting to enter the wave one lobby.
After the rework, the wave tickets are made tradeable.

The message when you "Read" the ticket.
The tickets are as follows:
Normal wave[]
- Barbarian assault ticket - wave 2
- Barbarian assault ticket - wave 3
- Barbarian assault ticket - wave 4
- Barbarian assault ticket - wave 5
- Barbarian assault ticket - wave 6
- Barbarian assault ticket - wave 7
- Barbarian assault ticket - wave 8
- Barbarian assault ticket - wave 9
- Barbarian assault ticket - wave 10
Hard wave[]
- Barbarian assault ticket - hard wave 2
- Barbarian assault ticket - hard wave 3
- Barbarian assault ticket - hard wave 4
- Barbarian assault ticket - hard wave 5
- Barbarian assault ticket - hard wave 6
- Barbarian assault ticket - hard wave 7
- Barbarian assault ticket - hard wave 8
- Barbarian assault ticket - hard wave 9
- Barbarian assault ticket - hard wave 10