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Introduction
To Tank generally means that the character or characters designated the "Tankers" will keep the aggro and damage of a particular monster or group of monsters while letting the other classes do damage. Tanking is often very important in raids and less important in standard PvE.
Tanks in Aion
Characters stemming from the Warrior school will most likely by the primary tanks, particularly Templars. Spiritmaster summons, particularly the Earth Elemental may also fulfill tanking rolls.