Went into the Duke's Archives, which just opened up for me. The area itself held a number of challenges: the regular enemies do a lot of damage and there are magicians which can do a ton of damage, most of which makes it through my shield. After a while, I made it through and entered the Crystal Cave, which is full of perilous invisible floors (hint: leave messages for yourself as guideposts) and some tough enemies. On the upside, the area just outside the cave is full of crystal golems which are not too difficult to kill and net you 800 souls apiece, so it's a pretty good area for farming. On the downside, when I finally made it to the boss, I got cursed, which means that I have to journey to the bell tower to buy a cure. Luckily, the warp feature will make getting there fairly easy, but getting back will require traversing the Duke's Archives all over again, although shortcuts should make it a little easier.