The classic “holy trinity” of MMOs is the tanker, nuker, and healer: One character to take nearly all the hits, only character to deal nearly all the damage, and one character to repair nearly all the damage.

  • Tanks typically have the highest hit points and the most armor, but the most essential facet of the role is the ability to concentrate fire upon themselves. This is typically accomplished via taunt mechanics: either an ability that forces the enemy to attack them, or a range of abilities that the enemy’s AI interprets as a disproportionate threat. Since most MMOs seem to have the enemy AI simply attack whoever has done the most damage to the enemy, taunt-based abilities tend to be treated as if they did high damage, even though the tank generally does far less than the nuker.
  • Nukers, or “DPS” classes, have a much higher damage per second output than the others. In certain games, their damage rating may be required to defeat certain enemies (as the other classes’ DPS is not sufficient to overcome these enemies’ healing rates). Traditionally, DPS classes are much less resilient than the tanks, and will be defeated much more quickly by the enemies if they catch their undivided attention. Thus, a tank is far more useful for keeping them alive and is far more economical to heal.
  • Healers have the ability to repair damage to ally HP in excess of that ally’s innate healing abilities and recovery rate. Without a healer, a group of tanks and DPS can generally only fight for a set period of time directly related to the incoming damage from the enemies: once their HP runs out, they are done fighting one way or another. A healer skews this limitation, able to compensate for damage. With a good healer on the team, the limit to the duration of a battle becomes much longer and is limited only by the speed of the healer’s recharge of abilities and endurance/mana.

A second trinity encompasses “support” roles: buff, debuff, and control. While these are often considered subsets of healing, they can be distributed among the other classes as well.

  • Buffing is the process of adding effects to allies that increase their power in certain spheres: generally attack or defense. A buffed character will generally take less damage and/or do more damage, effectively acting as a higher level while the buff is active.
  • Debuffing is the opposite of buffing: applying effects to enemies that make them deal less damage and/or take more damage. While debuffs are very similar to buffs, they aren’t balanced one-to-one: if a buff and a debuff were exactly equivalent in their effects, it would be more efficient to use the buff, as the intent is to defeat the enemy quickly, removing the debuff, while a buff might last through several fights.
  • Control is any power that restricts an enemy’s actions or movement. The classic controls are roots (which hold the enemy in place but allow it to continue attacking) and stuns (which completely incapacitate the enemy). Other control include fears (which usually keep the enemy from attacking but allow it to move and defend) and silence-type effects (which prevent the enemy from using a certain class of abilities). Some MMOs, like the original Guild Wars, include soft controls: an action is not impossible, but doing it is tactically unsound (e.g., making an attack deals damage to the attacker).

Most MMOs stick very closely to this model. The question is, do they do so because it’s a tried and true formula, or because combinations of the two trinities can account for nearly every action programmable for an MMO.

What effects outside the two trinities are possible, but rarely or never used?