Avoiding Aggressive MonstersEdit
Often you can avoid aggressive monsters by simply going around them, either in the same map or exiting the map and taking other maps. If you try to walk around them in the same map, you need to stay out of their Aggro range. This range is at least one square, and can be higher with higher-level monsters.
An aggressive monster will not attack you if you do not move, no matter how close you are. So when you arrive on a map and find yourself surrounded by aggressive monsters, you can stay still and wait for the mob to move away, then walk around them. Or if the exit point is visible you can usually step on it without being aggressed (this works best if you are a single square away from the exit point, i.e., if you've just arrived on the map). Or if you are impatient, you can use a Recall Potion.
A very useful way of avoiding aggro monsters is to turn the whole group into one character, by turning off Option menu -> "Performance" tab -> General heading -> Display all the monsters in a group. It is also wise to turn on "Show the grid" and "Display characters in transparent mode." The grid will allow you to see exactly how many squares away you are, and transparent mode will allow you to see any mobs hiding behind buildings or other obstructions. You may also wish to travel with your spouse, using the "Join" command. This allows you to jump to your spouse's position any time you are surrounded by an aggressive mob, rather than waiting for the mob to move away from you.
Here is a list of aggressive monsters.
Its not just walking that triggers, but also actions such as cutting a tree, for instance if an aggressive mob walks towards you and you end up being in their aggro range, and you are standing in front of a cuttable tree, cutting the tree will cause you to get aggroed.
In fact, even using a ladder, a door or a trashcan near a mob, even if they are not aggressive, will cause you to fight that mob as if they were aggressive.
It should also be noted that their aggro range is checked against the square you move TO and not the square you move from. So, for example, say you are 1 square away from a monster with an aggro range of 1. Moving away from this monster will NOT initiate combat. This piece of knowledge is especially useful when you factor in that you can move straight Up/Down/Left/Right, resulting in you moving a total of 2 squares away from the aggro group instead of just 1.
Moving in the opposite direction of a monster group will still trigger aggression.
An aggression between two aligned characters is called an Aggression.
See also: Wikipedia:Aggro.