Taliesin Downs 2 is supposedly the first 3rd party solo map for Myth 3:TWA. You can get it at MythMaps or from this direct link.
STORYLINE1000 yrs into the future our hero, connal, searches for a wizard the Wathcer's sword lost during the great war.He is forced to turn against a dwarven regiment of airships and paratroopers and so enters our hero escaping into Taliesin downs 2