The short stories and his comic surely did much to show hes more than a stoic grumpy general, but damn. Some of the interactions he has with other cards are really incredible. A few things I've loved when playing him in the game:
-Darius has shown to grieve when his brother (draven) dies in battle
-Darius has feared the day he and his brother would be on opposite sides (enemy draven vs darius)
-Darius flat out respects another general: the same general who adopted draven and darius into the noxian army ("If theres anyone who has earned their rank: it's you").
-Darius calls the legion marauders "a parasite to the empire". He hates everything they stand for, even though they're strong.
-Theres a specific card called the reckless trifarian. He quotes Darius when you play him, quotes such as "Nothing can stop me", and notably honors darius by saying "for the hand!". However, when you play them together their interaction is somewhat interesting. (RT: "Here to watch the bloodshed, sir?" D: "Here to win the war, soldier. Stand to."). Kinda shows how darius could care less about violence, he only wants whats best for noxus, and the best for noxus is victory.
Also: Darius straight up hates characters/champions who use mobility to win fights (such as zed). However, he has massive respect to characters who he views as strong (such as captain farron and tryndamere, whom which he has tried to recruit into noxus as he admired his strength).
No big reason for this post, just wanted to gush over how much detail they put into every champion's interactions in this game