Baseline (Widescreen) Solution & Issues
Ultra/Super-Wide (21:9/32:9) Specific Solution & Issues
What you need to do: Change the Aspect Ratio
Hex Edit the sacred3.exe -> look for 39 8E E3 3F and change it to CD 90 19 40
Fix also available from the PC Gaming Wiki Community Files (search there).
Eyefinity / Surround Specific Solution & Issues
Sidemonitors are black! When you start the game in Eyefinity you have to tab out and back in again to get it working, else you only have a Black screen and a mouse pointer.
The Ultra-Widescreen solution above can be adapted to Multi-mon but is ruined by the scaling of the HUD and menus. The UI is not only invasive and impractical but also downright broken in places: can't select a save file at startup, can't exit session to the main menu...
Hex values used:
9A99A140 for 6060x1200
00007040 for 3840x1024 (see Additonal screenshots)
4k UHD Specific Solution & Issues
Native support.
For some reason the framerate can be very low upon game start until you re-apply the resolution manually.