14 July. Legacy Mode allows players to switch to the combat system and interface from prior to June 2012 instead of the Evolution of Combat system. Player versus player combat Player versus player combat (PvP) can be performed in specific controlled mini-games and in an area known as the Wilderness. The Duel Arena allows players to stake money and items, while other PvP games offer their own rewards. In the Wilderness, players can engage in combat provided that their combat levels fall within a certain range of each other, and if a player kills their opponent they will be able to claim their opponent's items as a reward. Before December 2007, players went to the Wilderness to fight other players within a certain combat level range, hoping to kill them and gain their items. In December 2007, the Wilderness was altered to prevent players from transferring in-game items for real-world currency. PvP combat was removed from the Wilderness and temporarily restricted to new mini-games named Bounty Hunter and Clan Wars. Bounty Hunter was replaced by special Bounty Worlds on 6 May 2009 in which players were confined to the Wilderness and could be assigned specific targets to kill. "PvP Worlds" were introduced on 15 October 2008 where players could fight almost anywhere in Gielinor, but these and "Bounty Worlds" were removed when PvP combat in the Wilderness was restored on 1 February 2011. Non-player interaction Non-player characters (NPCs) populate the realm of Gielinor. Some NPCs, such as shopkeepers and some characters in quests, are unavailable for combat. However, most NPCs can be attacked and these are generally referred to as monsters. Monsters range from common, low-level creatures, such as chickens and goblins, to unique and often much more powerful monsters, such as the Queen Black Dragon, Telos, and Vorago. Most monsters have their own strengths and weaknesses, notable exceptions being certain bosses, which have no specific weaknesses. Demons, for example, have a weak defence against ranged attacks, while metal dragons have extremely high defence against ranged. The weakness of an individual monster is displayed in an interface above its model, along with its combat level and lifepoints. Monsters may either be aggressive or non-aggressive. Non-aggressive monsters ignore players unless attacked, while aggressive monsters may attack all players or may only attack players with combat levels below a specified level, depending on the circumstances or location. This can make certain areas