I was told on the Steam forums to open up a ticket for my crash in the second campaign misison here.
Win 10 64 bit
16 Gb RAM
nVidia GTX 970
Intel i5 2500k quadcore ~3.30GhZ
Right as the final wave including Lord O'Theland was about to be finished off, the game just froze for a few seconds and CTD'd without any further notice or message, and without me smashing any buttons or anything.
Customer support service by UserEcho