The new subclass for the Titan in The Taken King is called the Sunbreaker. You will have to complete some tasks to unlock the right to call yourself a Sunbreaker. This Destiny: The Taken King guide will help you find out where to unlock the Sunbreaker.
Where To Unlock The Sunbreaker Subclass Destiny: The Taken King
Go to Venus and follow the marker to the mercenary clan you are searching for, The Sunbreakers. Once you get to the marker, deploy you ghost and you will get a new way marker. Go up the stairs and out the door and you will find some enemies. If you are high enough level you and just skip past them but you might miss out on some of the new engrams. At the end of the path you will run into an Elite Hydra you will have to kill for the first part of the quest. Use your ultimate if you need to and your heavy weapon to make quick work of it.
The next part of the quest is to light a forge and wait to get your new Subclass. You will have to use the Sunbreaker Subclass to kill enemies for awhile. Once it you get to 100% of enemies killed, you will be this part of the quest and gain the Sunbreaker skill set. If you have bounties saved up for The Taken King, now is the time to use them.
Head back to the Tower to complete the quest and get some bonus EXP and Armor.
in Destiny: The Taken King Guides