As a tank class in Aion, the Templar is the most complete. If you wish to be the major meat shield in the game, this class would be a wonderful choice. They would bear the full brunt of attacks from other players in PvP and other mobs in PvE. It is their mission to fix all enemies' focus on them.
When it comes to defenses, the Templars are skilled at swords and shields. The sword can afflict damage on the enemies while the shield could protect the fellows from the damage from the enemies, though the effect is much less remarkable. Most skills of the Templar need to be performed with the combination of armor and weapon.
Perhaps it would a little bit disappointing to find that as a Templar, you could not become a dominant killer but only an assistant. However, though a little boring at the beginning, but in a team it is your job to provide assistance and leave killing to your teammates, and the role you play would never be less important.