Aggression
Aggressiveness or aggression, commonly referred to as aggro, is a trait in active monsters that determines attitude towards players in their vicinity. Aggressive monsters will target players within five tiles of their location on their own, on sight, to initiate combat, and are indicated by a red name.
Aggression mechanics
When aggressive monsters spot the player, a white exclamation mark '!' will appear above their heads and the monster will perform a brief action indicating they have spotted the player, giving the player a brief moment before they attempt to fight.
Aggressive monsters have an aggression radius of five tiles in any direction, equivalent to an 11 by 11-tile square centered around them. This is equivalent to the maximum range of the player's ranged weapon. Aggressive stationary monsters such as Floor Tentacles, Spiky Balls and Vipers are an exception to this, as they will only attack the player if they are within range.
Only one aggressive monster will attempt to initiate combat at a time. If another player initiates combat with the agressive monster before it can engage its target, another monster will instantly target the player.
If the targeted player initiates combat with another monster than the one about to attack them, they will override the initial monster's aggression and initiate combat with the monster of their choice.
Non-aggressive monsters, indicated by an orange name, are neutral and may be classified into active and passive monsters, depending on whether or not the player needs to be online to continue fighting them.
Strategy
If the player enters combat with an aggressive monster, they can quickly cast Immunity (default hotkey: ESC) to escape combat. Players may also drink a Fear Potion before entering aggressive rooms to prevent themselves from being targeted. Keep in mind that should an aggressive monster engage in combat with the player mid-Immunity cast, the cast will be cancelled, combat will begin and the player would need to re-cast the spell.
When entering an aggressive room, it is recommended to simply run straight through, using the aggressive monster's targeting animation to gain distance in order to avoid combat if possible. Gassy Cave and Moderate Mineshaft contain stationary Floor Tentacles which may be safely traversed by the player without engaging in combat, as shown in the image. However, combat is unavoidable in Quibble Lane, which contains Spiky Balls, due to its narrow pathways. As such players hoping to traverse Quibble Lane without engaging in combat must use a Fear Potion or Immunity.
Aggressive monsters may be used for semi-AFK (Away From Keyboard) activities, whereby the player can still pick up loot from defeating the monsters but does not wish to fully log out. However, the effectiveness of this strategy is limited by the Immunity timer mentioned below.
Aggression Immunity
When defeating an aggressive monster, the player will gain 30 seconds of immunity. However, this will not begin ticking down until the player moves or otherwise performs any action (including sorting their inventory, clicking on the tile they are currently standing on, and looting / opening loot menus). Moving the camera or the mouse in any other way that does not result in player movement or inventory sorting (including opening in-game overlay menus such as Spells, Settings, Map etc, viewing information cards, casting Sense, and switching servers) will not trigger the countdown. However, clicking on anything within the opened in-game overlay menus (any spell except Sense, applying knowledge points, or clicking on any button within the Settings menu) will begin the countdown.