Every MOB in the game has a hate list. This is how the game determines whom the MOB wants to attack. This list is quite large - enough so that there is no practical limit. Dealing lots of damage quickly is generally a reliable way to get to the top of the list, but there are many rules that govern the MOB hate list and other ways to generate hate (or aggro) besides dealing damage.
In the case of non-KoS MOBs, you can tell if you are on the MOB's hate list by considering it. If you are, then it will con as threatening instead of in the range [dubious - ally]. This is useful in conjunction with the feign death skills that some classes have.
A successful taunt instantly moves the taunter to the top of the hate list. This is achieved by assigning the taunter as much hate as the entity currently at the top of the list, plus one point.
A player is added to a MOB's hate list in several ways
- The player actively attacks or casts a detrimental spell on the MOB.
- The player taunts the MOB.
- The player attacks the MOB with their pet. In this case, both the pet and its master are added to the hate list, but the pet will be placed higher in the list initially.
- The player assists someone else attacking a MOB. This includes healing or buffing them (bard songs included).
- The player is KOS to the mob and passes within its aggro range.
- The player is on the hate list of a social MOB, and the MOB is near others of its kind. This will add you to the hate list of the other MOBs.
- The player is performing a quest that has a scripted event that creates 1 or more MOBs that automatically have the player on their hate list. (unsure of this one)
A player increases hate (and possibly moves higher in the list) in several ways
- The player does damage to the MOB.
- The player casts a detrimental spell on the MOB.
- The player taunts the MOB.
- The player buffs or heals someone on the MOB's hate list.
- The player sits down.
- The player begins casting a spell (sometimes referred to as casting aggro).
A player is removed from a MOB's hate list in several ways
- The player zones.
- The player dies.
- The player successfully feigns death and the mob has reset.
A MOB will attack whomever is at the top of its hate list with some exceptions
- The MOB is rooted, in which case it will melee whomever is closest.
- Casting a spell can cause some MOBs to temporarily turn to the caster. Usually (always?) it will attempt to interrupt the caster with a stun spell or bash, before turning back.
Managing one's position in the hate list is a very important skill. Players must be aware of the ways they and others generate hate. For example, during the the initial engagement of a MOB, it's crucial that everyone other than the tanks minimize the amount of hate they generate. This allows the tanks to build a solid position at the top of the list. As the fight continues it's important to avoid outpacing the tanks' hate generation.
This might need some more additions and testing concerning pets (/pet taunt, etc.) and summoning mobs.