Current questions and answers regarding the map editor.

What exactly does it mean to have mods in the editor? For example, I placed a hero on the map, changed his shared settings, and now he looks like a druid. If I upload this map to the internet, will he still look like a druid there? And also, if I create a new map later and place this hero, will he look normal again, but when I start the game, he still turns into a druid?