Threat is the numerical value which measures of a creature's aggression toward a character. It is used to establish a priority ranking of players, which the creature uses to determine whom to fight next in a group. This is referred to as the threat table, and (generally) creatures will attack the player on the top of the their threat table. When a player finds himself in this state (i.e., residing on the top of the table), it is known as having aggro.
The primary factor which determines a player's threat rating is damage. As a general rule, threat is generated at a 1:1 ratio with damage on the creature - the more damage done, the greater the threat produced. Note, however, that there are many exceptions to this rule.
Healing is another determinant of threat. As a player heals himself or others, he/she will generate threat that is split evenly among all enemies they currently fighting. However, this is often done at a ratio less of than 1:1. As a rule of thumb, a player will draw less threat via healing than he/she will via damage.
Other factors which will affect the threat value of each player on a creatures threat table include:
- Whether the creature is set to attack players within a given range.
- Debuffs inflicted on the creature by the player.
- Buff given by the player to other players or NPCs (such as pets) who are attacking the creature.
- Status effects on the player, such as invincibility, daze and death, which make him or her more or less favorable to attack.
- Threat generating or reducing abilities (such as taunts) used by the player.
- Time elapsed since the player last generated threat on the creature.
Tanks and Threat
Unlike other party roles, who work to avoid rising to the top of a creature's threat table, Tanks instead are trying to do just that. Indeed, it is the primary job of a tank to ensure that he/she is at the top of the threat table for all creatures that the party is fighting. Failure to do so is the most common cause of group wipes.
To help them do this, Tanks have abilities which generate threat at a ratio greater than 1:1. In addition, Tanks also have taunt abilities which will force a creature to attack them for a set amount of time, regardless of threat levels. Some of these abilities will add to their current numerical threat value against a mob, giving the Tank aggro by putting him/her at the top of the table. Other abilities, such as Taunt, do not actually generate additional aggression but causes the target to attack anyway. Without additional threat-generating action after this event the mob will return to its previous target.