The armory here offers practically all the best equipment in the game here for a hefty price, some are minor upgrades to your current equipment so make the choice of what to get for whom.
Hammer, Flame Whip
Shield Ring, Magic Shield, Heat Armor, Full Plate
Currently, you can only access two ladders other than the one you came from. The ladder below the one leading to the cave leads back to a previously inaccessible part of the first floor of the Cave. In here, you can talk to the blacksmith if you have both the Metal and Decayed Sword to get him to repair it for you (go kill some time after giving him the items, check out the castle if you want). The other ladder (which is reached by going east of the Item Shop) leads you back to the first floor of the Underground Market in a previously inaccessible part. From here, you just have to walk east to reach a ladder back up to a part in Deriju that grants you access to the Castle.
Information 1: You can't enter the castle from the front. Search out a hidden entrance.
Information 2: You can help an ill-minded person by giving them some Holy Water.
Information 3: Leave this town to the north, then take the stairs down. Go to the east 16 paces, and look at the south wall. There's a shortcut to Aisle.