How do you deal with a murderhobo player? The simple answer is to change your adventure format. That does not mean to avoid combat. You need to entice the players to solve issues without killing everyone.
The long answer? Well, The DM Doctor has your prescription.
So, you have one or more players who enjoy killing everything, related to the plot or not. This can be quite frustrating for a DM when players keep killing plot hooks and NPCs you intended to keep around for the long haul.
So what do you do about it?
1. Change the Adventure Format
What do I mean by this? Well, simply put, you need to back-off from adventures that focus on combat. You still need to keep some combat, but take a step back. This will most likely require more urban adventures and adventures where the players have non-combat tasks (such as puzzles like my prismatic puzzle and my puzzle of persistence).
In the case of urban adventures, make sure that players are aware of the local laws. In most societies, killing people (even evil-doers and BBEGs) is a crime. Though the heroes might have saved the town, they might be put on trial for needlessly killing someone (read humanoid in most cases).R
2. Reward “Peaceful” Encounters
Or maybe I should call these, “Peaceful Resolutions.” If your players solve an encounter through peaceful Roleplay, reward them. I know many books and references say to offer only half the experience points since there was a lack of danger. You do not need to bump this amount up, but you can reward the players in other ways.
Remember, the players are losing more than just XP, they are losing out on the treasure. Consider gifting them with information important to their quest or a surprise cache of loot. You can even have the would-be corpse act as a guide, follower, cohort, etc.
By providing unique and equal (or greater) rewards, your players will be less likely to kill every possible NPC. So how does this happen if they are killing everyone one? Well, perhaps down the line, the PCs learn they killed someone that would have been more useful alive.
3. Death Throes
All you Dragonlance readers and players know what I am talking about here. For those not sure what I am talking about, sometimes monsters have dangerous effects upon being slain (mostly the draconians).
Now, this is not to say that your monsters need to damage the party or destroy their items. The death throes I am talking about are of a different kind of beast. Just because your important NPC was killed, does not mean your plans are ruined (in most cases).
Consider the ramifications of the vacancy the players have created. Perhaps an NPC’s ambitious underling finds a chance to spread his wings and act upon his new found freedom. Perhaps he is an even greater threat now that the hand holding his leash is no more. Or maybe your NPC was favored by an even greater power. A power that wants to see things through to the end. Now your NPC rises with new granted powers. Remember, it’s not over until the fat kender sings.
Forget the arms race. Forget limiting options and overly restrictive house rules. You are not going to stop a muderhobo over night. But by carefully adapting what happens after the death of someone (or by letting someone live), you can adapt their mindset. A combination of positive and negative reinforcement will go a long way in allowing your group’s roleplaying experience to grow.
Now go make some awesome “Death Throes” for your plot NPCs. Those are the Doctor’s orders!
If you have innovative ways in dealing with murderhobos, share them. Or if you find that your particular murderhobos are out of control, just ask and we can come up with a tactical plan to correct your group’s particular issue. And if your murderhobos are metagamers, read up on Reskinning Your Monsters. Make sure to