Mythgard minimum requirements for Windows assume having at least Windows 7 operating system. Your processor should be Dual core from Intel or AMD at 2.8 GHz or a more powerful one. The minimum RAM requirement is 4 GB. As for a graphics card, it should be nVidia GeForce 8600 / 9600GT, ATI/AMD Radeon HD2600/3600, and it should support Direct X Version 9.0c. You also have to have 1 GB free disk space to install the game.
As for Mac OS, Mythgard requirements here start with Mac OS X 10.9+ operating system. Processor needs to be at least Intel Core 2 Duo 2.4 GHz. 4 GB of RAM is required. Your graphics card should be NVIDIA GeForce 320M. Finally, the game needs 1 MB of free disk space.