So I'm working on this alien race that is very similar to humans with some minor changes and one major change.
The biggest change is that they are very pain intolerant. This pain intolerance is apparent to them and when they started dealing with us it became more so. And with this particular aspect they actually started developing a lot of their cultural around it.
This is so that instead of a feature in them that got removed with time or they started actively working to raise their pain tolerance, they accepted it and started working around that. Because I know it might seem reasonable that they would just try to be more pain tolerant, but that is a part of the premise and I don't feel the need to change it.
Now the level depends on the person a bit but generally they are something close to 20%-30% of a pain tolerance of a human being.
And over the course of their history they started developing martial arts and fighting that is based on the concept of first strike and speed. That is if you are facing another of your own kind it all revolves around delivering a first strike, or in the rarest cases, a second strike and that's it.
Of course now they are space traveling people, and so they developed a complex and advanced means of fighting. And they mostly use armors to protect them. But so far they can't biologically engineer themselves to be more pain intolerant. And the rest I think is irrelevant.
Now my question is: Starting from what I said what is their biology going to be like, especially as opposed to us?
I don't know much about biology and so if it needs to be broken down to particular points I would do so, but it would be helpful to understand what those point are in the first place. And to make it clear I'm not looking for a detailed, hypothetical one I know, breakdown of their genes or nervous system. Just the basic stuff.
Example: How the Turians, Mass Effect, have this metallic carapace around their bodies because they originated on a planet that is exposed to a lot more radiation that others.
This helps in starting with the one problem I'm trying to solve: what is their biology going to be.