I just reinstalled Myth2 after almost 10 years of hiatus and remembered being able to play as the enemy on single player maps - I just don't remember how. Can anyone help?
well, if you mean having dark units in place as light then a simple tagset such as Reversal Reborn will do the trick.
but if you mean like where you have control as the dark and another has control of the light (because it only works online) that trick has not worked for many updates. but you can find plugins such as LvsD conversion that turns your coop maps to multiplayer, and takes out the script so you can play as dark.