Yhorm
Maximum souls: 401,533
Use the weapon art of the Storm Ruler. Before entering the fog wall, cast Sacred Oath and Deep Protection, equip Lloyd's Sword Ring, and charge up the weapon art of the Storm Ruler. Once the weapon art is fully charged and ready to be activated, enter the fog wall and start fighting. Aim the weapon art at Yhorm's head to ensure he would be staggered for an easy riposte. You can riposte Yhorm when he is stunned and his head bobs down nearly to the ground. The Storm Ruler is rather heavy. If your weight ratio is over 30%, you might as well equip the Mendicant's Staff in the right hand and the Shield of Want in the left hand, saving you some time after defeating Yhorm when you must quickly swap to soul-boosting items. Refer to the video below for the strategy.
