In The Black Throne, while heading to the Third Guardian, you will come across a bridge with spinning portals (The Black Throne, The Third Guardian III). When you reach the other side, you first be ambushed by a Rot Mauler and a Shield Lord. Defeat them and your next opponents will be one Shield Lord and four low-level soldiers. Do not kill the Shield Lord; instead, keep killing off the four soldiers and they will keep coming back, giving you as many souls and as much experience to max out your weapons as you want. To make things easier, run away from the Shield Lord whenever he gets close, and the four soldiers will follow (they are quicker than the Shield Lord so you should be able to get some hits in, run away when the Shield Lord gets close, hit the soldiers some more, rinse and repeat.