Agg is actually a couple of things, as people have pointed out above.
Pulling and agg; Read a Mobs description (Target Monster and hit T). If it says "May attack you on sight", that Mob is said to be an "Agg" mob. It will have a radius (longer in the front than in the back. It is NOT a cirlce, more of an egg, or a long elipse) of "Hate". Enter that area and you draw the Monsters Attention, and Will be attacked.
- Agg Pulling
- Damage Pulling
In Agg pulling you pierce the Monsters "Personal" space, draw it's attention and then PULL it to where you want it to be. You don't hit it, you just grab "Agg" and PULL. Honestly, this is where many new people mess up (and, Suprisingly, a good many "Veterans" as well). Don't follow a puller! You are doing the same, Basic, thing they are by following them, though, in many cases you are doing it unwittingly. Allow the puller to PULL!
Why not Hit it right off the bat?
Not all Mobs are aggressive (agg). But, all Mobs DO defend themselves, unless they are grey to you (Many grey mobs will run if struck, SOME, such as "Sided", or factioned, Mobs, and Spirits, and Dynas, will attack you if struck). If a Mob isn't naturally aggresive to you, you will need to generate that "Hate" another way, such as hitting them.
I once asked a friend if they knew how to pull, his response was;
"I hit, they come, what more is there?"
Ok...
One of the Cons of damage pulling is that many, if not MOST, Mobs are social, and will "Call" for help if they are attacked, and this includes being hit by someones damage shield, which is why some pullers will use their evade specials just Prior to pulling, or use something like a snowball (which was a holiday gift, and does NO damage to the one you throw it at). This is also why people without a damage shield of any kind can make some very good pullers, in some very tight spots.
Damage pulling carries the large risk of drawing many, many mobs down upon you. Agg pulling, on the other hand, allows the possibility of a very controlled pull. Provided the rest of the team doesn't interfer, and nothing goes wrong.
Agg and tanking.
As mentioned above, the TANK is the person who has "Agg". You aren't a tank if you aren't being hit, and you aren't being hit if you aren't highest on the hate list at that particular moment. Just because you are the tank, doesn't mean you will be a good one, though. So, the job of the "Tank" is to make SURE they are the most hated in the group, and, if this changes (Say an Agent gets off a particularly powerful Aimed Shot), then it is the Tanks job to grab that agg back again, ASAP.
In general, you don't want "Squishy" targets to be the tank. You want tanks who have the tools to deal with it such as;
- AC / HP (the two go hand in hand)
- Evades (HIGH evades, coulpled with HIGH Add All Def)
- AC / HP / temp Invulnerability (I'm throwing soldiers in because they CAN tank, yes, there are often many soldiers who can't, for one reason or another, but the same goes for Fixers, Enforcers and Shades as well).
Another element is the ability to grab agg and hold it, as well as to take it back again if lost to a heavy Burst, strong Aimed Shot, or Complete Heal
- Enforcers have Taunts
- Shades, and the others have damage (and some have minor taunts as well, but still rely on damage)
Taunting is One VERY good way of generating "AGG", or Hate. Early on Forcer have Mongos (look Mongo up on Auno.org), and this is often good enough. Later on an Enforcer will invest in Perks which Taunt, Procs which Taunt, and items which Taunt. They have More taunts than any other class, and have the ability to "Stack" mobs when neccesary.
Damage is pretty much self-explanatory; Hit a Mob and the more damage you do to it, the more of a threat you are, and the more the mob will "Hate" you. Shades are pretty much the Kings and Queens of Damage. There are times when a shade will Outdamage their entire team. And, by this, I don't mean they will do MORE damage than anyone else, I mean they will do MORE damage than the rest of the team... combined. That's some sick damage, and it's a good way to rise to the top of a Hate list (ask Forcers!
they pretty much hate us to!)
Healing is another way to draw "Agg". The Complete Heal is one of the heaviest, single Taunts in the Shadowlands. The upper Mongo is a 10K taunt, and won't make a DENT in the hate list of a creature fixed on a Doc who just cast a complete Heal, BUT! Hate builds. If a Forcer is taunting regularly (With Procs, Perks, Items, and SOME Mongos), then they will have built a good deal of Hate, and it will take a good deal less to draw agg from a CHing Doc, but, if they are starting cold... forget it.
Same with Shades. I dinged 200 on my Shade in Adonis, fighting hecks. I was in a group with two Docs, and One other player. One Doctor had expressed a desire to "Die" in order to keep from dinging, and so end his night with a Pool. Towards the end of one of our last fights, he decided to CH
and die that way. Didn't happen! There was enough Hate built up from all my shades damage that he only took a couple, few, hits, before I got it back (Back Stab FTW!). Next fight he DoTed himself and THEN CH'd!
So, Agg is VERY important to AO, core element, if you would.