I really wasn't expecting the writing to be the star of a Diablo game, but holy heck. The characters, the moral ambiguity, the story...it's all kinda fantastic. Lilith is such a terrifying and complex villain, and the story itself explores these themes of abandonment, parentage, power, faith, and free will that were so, so spicy...at least more than usual for a game like this. The writers did not have to go this hard.
Plus you know the writing is good when you seriously don't know if you would have said "no" to joining the villain or not.
Favorite quotes:
"You will experience pain only glimpsed in myth"
"The dead are owed nothing while the living continue to suffer."
"I was attacked, obviously. By vast quantities of alcohol, wielded by my own treacherous hand."