Aggressiveness (or hostility) refers to the behaviours of various monsters in RuneScape when in close promixity to players. Aggressive monsters will attack players; some are aggressive based on players' combat levels and others are aggressive regardless of level. Aggressive monsters can be particularly dangerous 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 less than or equal to twice the monster's level. If the player's combat 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 × 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.
Different monsters seem to have different levels of aggression; some, such as Jungle horrors, will seek you out from many spaces away, whereas others, such as Mountain trolls, are aggressive on a smaller radius.
- 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. Note that logging out is not classed as leaving the area, so if a player logs out and logs back in again the monsters will still be tolerant.
- 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, as well as those encountered while Dungeoneering, are aggressive regardless of level. All primates on Ape Atoll exhibit this quality as well. In addition, guards will attack players whom they catch thieving from stalls anywhere on Runescape regardless of the player's combat level.
- God Wars Dungeon monsters are agressive only if the player is not wearing a corresponding god item (e.g Saradomin spiritual mages will not attack if you equip a Nex item or Saradomin item).
- The only exeption is the Zaros area, where all monsters are agressive there.
- Revenants can be made tolerant for an hour by using one charge of a Forinthry brace, or by staying in one area until they become tolerant.
- With current maximum combat levels, the minimum level for monsters to be aggressive towards any player is 100 (maximum player level being 200). However, some monsters with a high combat level (101+) can be nonagressive at a specific level, such as Elite Khzard Guards (who are tolerant at 173+ combat).
- Most Slayer creatures are passive, despite the player's combat level. This does not apply to all however, as Kurasks, Gargoyles, Warped terrorbirds, Dark beasts, and Aberrant spectres (in the Slayer Tower) are aggressive.
- The Elite Dark Mages/Rangers/Warriors and Elite Black Knights will always be aggressive to players not wearing full Elite Black or Dagon'hai armour.
- Desert Bandits south of Bebadin Camp will always be aggressive to players wearing Saradomin or Zamorak items.
- Desert Bandits (to players not wearing Saradomin or Zamorak items) and Al Kharid Warriors are both passive until a player attacks one. All of the other warriors or bandits in the vicinity will then attack that player because both areas are multi-combat.
- The aggressiveness of many NPCs is different than on RuneScape Classic. In the latter, some non-aggressive NPCs will not chase after the player if the player attacks and then retreats; on RS2, most NPCs will follow the player. Also, some monsters, such as scorpions and hobgoblins, will fight to the death on RS2 but will retreat on RSC.
- Creatures that never become tolerant provide excellent AFK training opportunities, such as Dark Beasts (90 Slayer required) and Desert Bandits.
- Opening the Squeal of Fortune will not cause passive monsters to become aggressive again.