O.T.T.O is the Master Builder latest invention, a new builder available on the Builder Base.
Once you have unlocked O.T.T.O you will be able to choose if the Master Builder stays on the Builder Base (so you can use 2 builders there) or on the Home Village (bringing to max builders up to 6).
To unlock O.T.T.O you must have a level 5 O.T.T.O Hut, which requires a Builder Hall level 9.
This upgrade is not done with resources and doesn't take time, all you have to do is to complete tasks on your village:
|Level 2||Gear Up all 3 buildings: Archer Tower, Mortar|
|Level 3||Upgrade Cannon Cart to level 18|
|Level 4||Upgrade Mega Tesla to level 9|
|Level 5||Upgrade Battle Machine to level 30|
Once you reach level 5, O.T.T.O will be unlocked and will work as a second builder. With a second builder available, the Master Builder will be able to travel to the Home Base.
With an extra builder, the Master Builder will finally be able to travel without issues to the Main Village and work as a regular builder over there, becoming the 6th builder of the Home Village.
However, to be able to travel to your Main Village you must first place the Master Builder Hut on your Home Village:
Well, now it's done! Now you can travel the Master Builder to your Home Village!
You can bring the Master Builder back to your Builder Base at any time, as long as you are not using all builders at the same time on your Home Village.