You can combat PKing by becoming a God and punishing PKers, or you can have a "natural"/automated system which punishes PKers. It is very disappointing that so many people decide to go into such a Role as a PKer, but there is little that can be done to stop those peoples mentality. What can be done is to implement a system that would force Player Killers to behave, but that usually means imposing rules on the game that makes it difficult for situations such as duels. There is one way of doing this that I have been pondering on for a while. If you implement a virtual "law enforcement agency" with certain laws that prevent fighting [and specifically killing] in the streets (as you would have expected in the medieval times). You then have NPC guards who can "overpower" the PC (without attacking and knocking them out, like in "Might and Magic") and drag them away. There is a "case" heard about what happened based on who started the fight. Whoever dealt the first blow is the offender and gets punished accordingly. There could be an Arena where duels could take place for public entertainment that would be devoid of such rules. It would also add a random element as to what kind of skills the character you got pitted against had (so that is where the word pitted came from). The other benefit of the arena is that it adds a roman element to a medieval game, which could do well for the atmosphere and other such elements in the game.

I have seen other methods of removing the Player Killing factor in Diablo II where both of the players are required to click on the "Aggression button" before they are allowed to trade blows. The button can only be pressed when the player is IN TOWN, which then also removes the coward element of chickening out when you are almost dead. It certainly was an improvement from Diablo (the original) where you were killed more often as not by friendly fire in the back from a "helpful" Rogue (note that I was a Warrior). At least in Diablo II, if you have an Amazon standing behind you when in a friendly mode, fire from her bow does not damage you. I find this helpful, because I am there mainly to take damage [away from the Amazon] and let the Amazon kill to get us the Experience Points.

Another way to indirectly punish Player Killers is to use the Reincarnation or Possession systems (discussed in "Timing in games" or "Old age in games"). Base on some recorded data on how that player has been going through there last incarnation; they get placed in an appropriate new incarnation. It follows a similar law to the pathway to Nirvana:

• If they achieve something good in their lifespan, they can expect to have some kind of increase in status in their new incarnation (such as the ability to learn a new skill).
• If they have not achieved enough in a lifespan, or have achieved something bad (considered bad by the game – such as Player Killing) then they could lose the right to have certain skills in their new incarnation.

You may want to expand those two points into a longer list that includes steps and has a "neutral" choice in it, but I think that the two points there describe the consequences of actions in using the system, and sum it up quite nicely. You could explain the same thing using the Possession system using the following:

• "The players mind has been corrupted by the evil and the consciousness transfer lost a certain ability"
• "The players mind has been blessed with clarity and as such has gained a new ability from the new host"

I would prefer to see actions and consequences in games and also reasoning for what happens. Reasoning is something that is often just overlooked or thought of as specific hassle. If these issues were addressed, then the game would be a much more enjoyable experience for everyone. If a game explains why it uses something, then it gives added depth to the entirety of the game and will definitely be remembered for its finer attention to detail. This is providing that the entire game includes attention to detail.

If you wanted to remove PKing altogether, using an aging and death system (as mentioned in the appropriate topic) you can then remove attributes/statistics from players that continuously kill others. This is a little harsh in my opinion, but effective. Personally, I like the alignment and karma idea.