This game may encounter graphical issues on multiple monitor setups.
You may experience duplicate images, stretching, resolution problems or offset graphics.
This is currently caused by a limitation in multiple monitor support in Linux, two workarounds exist:
1) Try running the game in windowed mode. Most games offer this setting natively inside the options menu or launcher, or it can be forced by changing the appropriate lines in configuration files.
2) Temporarily disable your secondary monitor. You can do this through your system options, or by simply unplugging the device.
You can find a bit more information about this issue in our Linux Support FAQ.