So I'm going to preface with I have NO programming skills or knowledge, so I have no idea if this is something that is even feasible. I just had an idea to put out there and Pantheon seems like they actually listen to their fanbase. Also, if it's a technical impossibility I'd be interested to know why just because those things interest me. So the idea:
When you die in a zone, the zone spawns a doppleganger of you. That mob is equal to you in every way. Your double is KOS to you zone wide, and non-KOS to everyone else. As long as that double is alive, or for a period of time (say 1 week game time for instance), you have a 10% exp penalty. To prevent someone from overloading a single zone with their own doubles, subsequent deaths increase the strength of the double by 10%, increase it's duration until despawn, and increase exp penalty, to a cap of 50% or somewhere there abouts, but does not spawn another entity.
There are a couple social aspects to this. Your group would have a vested interest in killing the mob since it will KOS you zone wide when you go to that zone, so you know if you want to fight there, you're going to have to deal with it. Also, people could equip "bounty" gear, player crafted, and hunt people's doubles for them, with the gear giving a bonus versus this specific mob. It may be a good way for people to have something to do when they only have an hour or so to log on, is pop in and earn some cash killing doubles that are now too powerful for the person to tackle. There could be a money sink component where an NPC will summon the mob to a special arena in the larger cities and you can fight it there with help from bystanders, for a price (the cost of the summon being level dependent). I actually think it would make raid wipes more interesting and actually a bit more painful, because you'd have to clear all the trash mobs upon entry if you had a large raid wipe in a zone, so it may prevent "zerging" as a raiding option.
Like I said, just trying to be creative about one of the more obnoxious topics that come up in MMO's. You either make it so painful (early EQ corpse runs to the bottom of The Hole naked) or so easy (every other MMO since) that it's essentially trivial. This way would make you work for it a little bit, or have a friend or two.
Pantheon guys, if you read this and want the idea it's yours =) Just name the summoner after me, that'd be awesome.
Thanks for reading and can't wait to get my hands on this game!
Cyonide Wolfpaw - Soon to be likely Shaman.
While I appreciate the idea Cyonide, this topic has many threads already based on idea's just like yours, I will link a few below so you can copy/paste your idea in one of them as this one will need to be closed.
I found these by typing Death Penalty into the search function;
https://www.pantheonmmo.com/content/forums/topic/2087/let-s-talk-death-penalty (8 pages, posted by me, asking the community their thoughts)
https://www.pantheonmmo.com/content/forums/topic/3260/death-penalty-idea-s (thread in Champions section - MMO design theory)
https://www.pantheonmmo.com/content/forums/topic/1299/the-sting-of-death (2 pages even after necro and prior 2015 posts archived)
https://www.pantheonmmo.com/content/forums/topic/3116/the-fear-of-death (low responses as this topic has been discussed a lot)
https://www.pantheonmmo.com/content/forums/topic/2558/making-death-impactful (2 pages based on someone's idea, like yours)
I see it is your first post, so welcome to the forums Cyonide, please use the search function before creating a new thread as we have been around for almost 2 years now and a lot of things have already been discussed. ;)