Kill stealing is just what it sounds like- one player taking a kill away from another player who has done all the work. It is a problem faced by many MMORPGs. Guild Wars has done away with this problem by making all Explorable Areas uniquely instanced for each group that enters it, so there is no camping of monsters spawn spots. Additionally, players get no bonus from killing a monster (or enemy player), all experience and loot is shared by the party.
However, combative NPCs can killsteal the player/party. If an NPC deals over 50% of the total damage on the enemy, the kill (and rewards) is attributed to that NPC rather than the player. This is noticable early on outside Foible's Fair in Wizard's Folly where the Academy Monk will often engage the nearby Ice Golem.
While it is not possible to kill players to steal their loot, it is possible to steal their loot. Loot is normally assigned to particular players, which means no one else can take it. However, loot becomes public (available to all) if the assigned player doesn't take it for ten minutes. This presents two scenarios:
- If a player overlooked a valuable drop. Others (who noticed the item) may not tell that player and wait for several minutes before running back to its place and picking it up after it has become available to them.
- If a character is killed, and loot drops for that character, the live characters can simply wait a long time without resurrecting the dead player, and then take his/her item. This is obviously most easily done when there is only one player left alive.
This is extremely parasitic and will probably cause the robber to end up on many players' ignore list as well as possibly having the whole "indiscretion" announced on public chat if the victim sees the robber in a town later on. This could make joining parties very difficult.