Happened to me when I was working on the Orange skill.
When ever I use him with other heroes, the game crashes on second or third wave especially when she activates her white skill.
To complete the last task, I had to run campaign solo.
It also crashes in expedition with the same scenario.
The team that causes crash was Satyr + assassin + angelic Herald. I don't remember the other two.
I was trying to finish Herald Orange skill and assassin at the same time in expedition.