This is a GFX driver issue. The best solution is to update your drivers and then restart your computer. If you are unable to update your drivers or the problem persists then follow the steps below.
1. Navigate to the 'Library' section of Steam
2. Right click 'Hack, Slash, Loot' and select 'Properties'
3. Select the 'Set Launch Options...' button
4. Enter 'd3d7' into the text field and then click 'OK'
1. Create a short cut for the game
2. Right click the shortcut and select 'Properties'
3. In the 'Target' field add ' d3d7' to the end of the exe path
You can also enter 'd3d9' if 'd3d7' doesn't help.