This pisses me off to no ends! There are so many bosses in Dark Souls I wish I didn't have to kill and Sif is the most important of them! Even when I didn't know about his story then, it just felt SO wrong to fight him when all he was doing was guarging his master's grave... But after learning about his whole backstory, it's even worse!The DLC did make the fight more meaningful, but at the same time, as impossible as it may sound, fighting Sif became even sadder since now, not only did you save him from the abbyss, but you have no choice but to fight him after he finally remembers you! I mean it's so sad...He only fights you so you won't get corrupted by the abyss and suffer like his master, because he loves you enough to die for your own protection... So many tragedies happen in that game, thank you for honouring these incredible characters with your fanart, I'll definately stay around to see more of those :')
I actually don't believe he was trying to protect you. I know a lot of people say that but I think its a little baseless. To me it looks like he remembers you and is sad that he has to fight you, and although he is conflicted he chooses Artorias. I think its very admirable that he is still loyal to his long lost companion/friend/master. well thats my 2 cents.