Labyrinths of the Mind

The map is interesting to play, but I got stuck in the starting location. I cleared almost everything, but it's unclear where to go next: on one side, there's a stone blocking the bridge, the mine leading underground doesn't work, and the dwarf treasure with the pyramid also seems to have nothing interesting. You can't pass through the blue tent without a key, and it's unclear where to get it. There's also a garrison with 60 titans (colossi), which is impossible to take with my current army and spells. What am I doing wrong?