Knight
Knights favor close quarter combat, sacrificing the safety range provides to charge into battle. The ability to equip heavy armor and heavy shields and increased constitution makes the Knight an ideal choice for tanking (taking heavy damage), but they also possess extensive weapon training allowing them to equip two handed swords which makes their physical attacks, which are already powerful, even more devastating. Knights are ideal for aspiring tanks and players who enjoy up close and personal melee combat.
Advanced Classes ~ Level 36
A combination of the most powerful versions of single and multi-target taunts and the highest constitution available to any class makes the Solar Guardian a great choice for tanking in Lucent Heart. A powerful array of offensive abilities including an attack that hit multiple targets, slows them, and increases the chance for them to be critically hit, not only makes the Solar Guardian's job of holding the attention of multiple enemies easier, but also makes them formidable contenders in the role of dealing damage.
Celestial Templars retain their ability to wear heavy armor and gain the ability to equip unique gun shields which not only provide the same types of protection as other shields but also come equipped with cannons of varying effects that can be used against enemies in battle. There is no need to shy away from tanking as a Celestial Templar if that is what you are interested in because what a Templar lacks in constitution it makes up for in its ability to reduce an opponent's attack power with a single, heavy handed blow. A Celestial Templar is also perfect frontline commander with the ability to appoint specialists from each of the three branches which provides unique bonuses to selected teammates.