Hi!
Thanks for the kind words - glad you're enjoying the game!
As for the fallen champion - I haven't played the game myself in a while, so I don't remember how I used to fight them myself, but from what I do remember, plus looking at the code: it's the strongest non-boss humanoid enemy, so you may need an end-game character to beat them. As they're immune to magic, Combat 2 and high Brawn are actually very useful. Because of the healing and permanent damage buffs, it's essential to focus on high physical damage (def. try to get a legendary weapon - I'm also trying to avoid big spoilers, let me know if you want more hints on which weapons would be the best and how to find them), use Fortify on yourself. You may also try to use evade when the champion readies the big attack. Stun immunity will be helpful, and if your weapon damage is too low, but you have a lot of silver, Bottled Explosions can deal with almost anything in the game.
Hope this helps!