Here's a taste of the new features you can expect in Myth II 1.5.1:

Native support for modern hardware, higher resolutions, and graphics acceleration via OpenGL and DirectX, while still catering for legacy systems.
Numerous bug fixes eliminating many causes of crashing and Out of Sync errors, resulting in the smoothest and most enjoyable Myth experience ever.
A new Autohost feature, allowing automatic hosting of a playlist of maps in multiplayer.
The ability to view the currently active plugins in multiplayer games.
New mapmaking enhancements to allow for even more creative variations of gameplay in 3rd party add-ons.