One of the most challenging aspects of the game is grouping to do big private instances. This can be done in six-man fellowships, such as Fornost, Carn Dum or Ann¨²minas. There are also harder instances for raids like The Rift (12 people, or a double fellowship) or Helegrod (24 people, or 4 fellowships). Due to the difficulty of the encounter and the many players involved, the seven classes will get a specific task by the raid leader.
A guardian will most likely be assigned to tank the mobs, whether the boss or some adds, thus protecting the rest of the raid from getting damage. Multiple guardians can share the load, making it easier to keep them alive. A captain can also be assigned to tank, if no guardian is available, but he will more likely be chosen as off-tank, taking care of mobs that the guardian missed. Aside from that, the captain's main job is to keep everyone buffed and remove fear effects. A champion can also be used as tank, but like the captain, he is more likely an off-tank. His area of effect skills can also be used to damage several mobs at once, and his clobbering attack should be used to interrupt mobs when they use a special attack. The hunter's job seems easy, damaging the mobs as much as they can, but as the main damage class they have to be careful not to take the aggro away from the tank. he should also cure poison on his fellows. A burglar's main jobs are to use his tricks to debuff the mob, start conjunctions and do damage. The minstrels take care of healing the raid to full morale, while also watching their aggro. A lore-master takes care of the crowd-control, keeping away mobs from the fight. Also very important is that he provides power for the raid. Lastly he must cure diseases and wounds, and give stun immunity when needed.