When playing an advanced Knight, in Ab'Dendriel, there is a small castle called Elven Bane. It is northwest of the Elven Fortress. In ElvenBane's basements, you will find good monsters to level on and some armor called "Chain Armor", which you can sell to the the NPC in Ab'Dendriel for 70 GP. When you level to 20, you should be able to fight most of the monsters in the entire castle. You should at least be level10 and have the following equipment for your character to survive:

Soldier Helmet
Scale Armor
2 Handed sword
Brass Legs