https://bugs.winehq.org/show_bug.cgi?id=43995
--- Comment #21 from debianxfce fin4478@hotmail.com --- AC4 crashes after the Fireship mission when the game is starting the next mission. Fix: add AC4BFSP.exe to winecfg applications and set the dll override for d3dx11_43 (builtin,native).
I figured the solution from this crash trace: Modules: Module Address Debug info Name (226 modules) PE 340000- 37f000 Deferred d3dx11_43