OP here, sorry I disappeared for a bit
He's exceptional, but not more exceptional than you'd expect. He's got the perfect storm of traits that led to his situation. His magical alignment, where he was, and his particular situation aren't exceptionally unique, but the combination of his traits, led to this.
That was what I was going for. He was a knight for quite a while, and he had to live through the great war, which as an immortal, he survived, but had to watch a lot of his friends die painfully.
>What did he do that's causing such severe mental anguish?
He started his life off as a knight, thinking he's going to be this noble bloke who goes gallivanting off about using magic to save people, and then he witnessed both World Wars, which seriously changed his opinion on war, and realized that the things that he was proud of were actually monstrous atrocities.
And yeah, he expresses his PTSD mostly in anxiety, and violent outbursts. I've been trying to keep him going through character changes, as one who'd been alive for hundreds of years would.
His skillset mostly, as you've said, comes from experience. The difficult was that I could really justify saying he DIDN'T have these skills, given what he's done, so I just tried to make it tragic with the angle of, "he's got these skills, but laments their use", which honestly may just end up making it worse.
Would be a good idea, but there's no astral travel in setting. There are things much more powerful than him, (think Lovecraftian entities) but they don't appear for a good long while, properly anyway.
One of the things I try really hard to do is make everyone justified. People are justified in hating/opposing him because he's an imperialistic (literally, he was a soldier of the British Empire) mass murdering, borderline psychopath. Bit difficult when the bad guys are the Nazi's but hey.