Haha sorry about it! I also noticed that could happen when I was testing but I just assumed it as part of the adventure in the labyrinth... there are 15 batallions in each labyrinth so a good trick is to finish one labyrinth and then check if you got 15, that way you know that you finished that section. There is no story after that, as you say, it's just free play and get the achievements of the tower :) Thanks for playing!