As an alchemist, have a maximum level Fire Bomb and bow and arrows. Keep running from the Shadow Lord since you are faster than him. When he is near you, walk around him and lay Fire Bombs to do about 300 damage each. Drop about six bombs, then run away. When you are a good distance away, use your bow and start firing in the direction of the Shadow Lord. When he is close, repeat the Fire Bomb tactic before running away. Repeat the same strategy. Constantly doing this will greatly reduce his HP and eventually kill him.