After losing 26000 souls (not as bad as it sounds for a level 50 character), I was forced to backtrack to the magic shop in Darkroot Forest to buy a spell that let me pass the two bow-wielding knights without getting killed. Unfortunately, I found out that those knights are not, in fact, black knights, but silver knights, which are essentially slightly weaker, respawning brethren to the black knights. Luckily I discovered a bonfire and later a shortcut back to the front so I don't ever have to deal with the pair of giant arrow-slinging knight again, even if they do come back. I made my way to the bosses, a pair of bronze knights named Dragon Slayer Ornstein & Executioner Smough (but I call them fatboy and slim for reasons that are obvious once you see them). The tricky part about this boss, on top of there being two of them, is managing the enemies radically different attack patterns at the same time. I didn't manage to beat the pair, but I have a strategy that I think, with some luck, will let me defeat them without external help.