See also: Tolerance
Aggressiveness is used to define how certain monsters in RuneScape behave when around players. Aggressive monsters will attack players; some are aggressive based on players' combat levels and other are aggressive regardless of level. Aggressive monsters can be particularly dangerous when in a multi-combat area with multiple monsters. Non-aggressive, or passive, monsters will not attack players unless they are attacked first.
When aggressiveness is based on combat level, an aggressive monster will attack a player whose combat level is twice or less the monster's level. If the player's level is more than twice the monster's level, it won't attack.
For example, a level 51 player enters an area with a level 28 Hobgoblin. Since the player's level is less than twice the monster's level (28 X 2 = 56, which is more than 51), the hobgoblin will attack the player. Conversely, if a level 105 player enters an area with a level 28 hobgoblin, the monster will not attack because the player's level is more than twice the monster's. In this case, the hobgoblin will ignore the player (unless, of course, the player decides to attack the monster). The player would need to be level 57 or higher to avoid being attacked by the hobgoblin.
- After a player spends a certain amount of time (about 10-20 minutes) in the vicinity of aggressive monsters, the monsters will become tolerant of the player and become passive. If the player leaves the area and then returns, the monsters there are aggressive again. This includes Random events that teleport players from the area and then return them.
- Some monsters that become tolerant may become aggressive again, after a period of time, even if the player constantly stays in the vicinity. For example, Flesh crawlers in the Stronghold of Security and Kurasks in the Fremennik Slayer Dungeon are this way. Other monsters do not spontaneously become aggressive again no matter how long the player remains in the vicinity.
- Most monsters in the Wilderness are aggressive no matter what your level. A few, such as Rogues, are not aggressive.
- Some monsters in the Stronghold of Security are aggressive to any player. These include Flesh crawlers, level 50 Giant spiders, and level 37 and 59 scorpions.
- Aggressive monsters with a combat level of at least 69 are also aggressive to any player, as 138 is double this, and it is impossible for player to have a combat level higher than 138.
- Most Slayer creatures are non-aggressive, despite the player's combat level. This does not apply to all however, as Kurasks, Gargoyles, and Aberrant Spectres (in the Slayer Tower) are aggressive.