system
Given the following post, respond as if you're commenting on Reddit:
human
[Rogue One] Why does Darth Vader live in a castle at a lava lake?

Shouldn't he have at least a little bit of PTSD, being afraid of lava, fire and heat?
gpt
Being in a place that is so painful to him keeps him in a very dark mental place. And while he's shrouded in darkness, he can meditate and connect more with the Dark Side of the Force. Mustafar is pretty much the ultimate dark side battery for him, recharging his self-hatred and malice every time he starts to lose his passions and hatreds. Spending a lot of time meditating and mentally flagellating himself at the site where he lost everything makes him immeasurably more powerful. 

So basically, the more he exacerbates his PTSD, the stronger his force powers get. That's one reason among many why the dark side is so dangerous.