Instructions
Build a shelter, which produces lumber harvesters. Lumber is a required component of most structures.
Select your harvesters and click on a group of trees to begin harvesting lumber. Allow 150 units of lumber to accumulate.
Build a Hunters' House, which costs 150 units of lumber.
Wait for a fellow Builder to die. At least one tends to die early in the game, before proper defenses are set up, so the wait should not be long.
Select the Hunters' House and click the option to train a Titan Hunter, which transfers a unit from the Titan's team to the Builders' team.