I did not use the theif's ring with Flame Lurker, I just decided to go against him using melee attack which resulted in sucking over 3 hours of my life to beat him and more than that on NG+. At that time I wasn't aware of the magic and arrow trick and even if I was i wouldn't use them because that ruins the game IMO
Flame lurker was my favourite boss fight. I literally jumped up from my couch and fist pumped when I beat him on melee combat. Best gaming feeling and moment ever!! Demon's Souls made you care sooooo much about your character's life. Your character's life meant so much to you because it took you back so far. It almost felt like your real life was interlocked with the character's. Other souls games are fun, but I care less about my character's life. Bloodborne is the only other Souls-ish game which is as satisfying as the origin Demon's Souls.