Heroes 6 - Discussion

Hello everyone. Has anyone played Christmas Treasure Hunt? I collected all the artifacts, but I don't know what to do next. I've searched the entire map.

And how do you play it? I put it in the Scenario folder, and in the game, when choosing "scenario," it appears, but the "start game" button is only active for a few seconds, and then it turns gray. Even if I manage to click it in those seconds, the map still doesn't start. :(