Empath
Caring too much about people's problems and you.
So you've decided to mostly give up a life of killing shit.
What's it do?
Empath is basically the ultimate mutation for those who want high focus and nonviolent skills, and comes with a variety of advantages and disadvantages.
The biggest one is being unable to kill anything even moderately sentient, as it'll give you a fairly large amount of stress and put you and shock depending on your focus skill. So you're probably not going to kill anything anymore, really, unless you've got enough focus.
On the upside, you get bonuses to brains, senses, focus, and medic, as well as being better at using the medium mutation's seek command. And beyond that you also get the massage command, which can destress other players. You also get soothe which allows you to destress as well, and also absorb any mental illnesses the target has. You may end up with their mental illnesses if your focus is too low, but if it's high enough it'll be eliminated all together. As an added bonus, your stress level fluctuates based on the highest stress level in the room, so you can see exactly how stressed someone is.
So, I can't kill shit at all?
Nothing's stopping you from killing non-sentient things, although the admins sometimes have a weird idea of what constitutes "sentient", basically if it has some sort of emotion aside for "Raagh I kill you.", then killing it will probably hurt you too.
Can I help my friends out in the field?
Generally you're not really kept from providing sideline assistance, although the death issue does make things rather complicated, and one of the other effects from empath makes it so other people's stress also stresses you, so if they use a lot of focus mutations you're going to get incredibly stressed.
Well, I still want it, how do I get it?
There's not much I can say about it that won't be spoilery, but it really helps to have a lot of climb, someone who can craft, you or someone else, and the ability to tear through a bunch of zombies. Talk to Guru, and you'll get on your way.
Anything else?
Well, lastly, I can't stress this enough. Do not get empath unless you have a ton of focus, or else you're going to find it incredibly fucking annoying to have. I had empath at an incredibly low focus and I was getting stress and shock from my apartment, from stuff being killed dozens of rooms away.