you can try at Shrine of storm 4-1, equip with avarice ring... then slay the rolling skeleton up to the wall area... then go back..to nexus.. each time u do that.. u will get 2000++ soul

on 4-2 .. bring bow and snipe the death reeper .. each time u do that go back to nexus... and u will get 5000++ soul

if u can go to 4- 3.. just use storm ruler to kill all the stingrays.. 1 stringray will give u 1500 soul... there will be many there... so total u can get each time go there around 20000 souls

summary:

Rolling skeleton ( 4-1 ) = total 2000 soul

Death Reeper (4- 2 ) = total 5500 souls ( need to slay adjudicator first )

Stindrays ( 4-3 ) = total 21000 souls ( need to kill old hero and storm king first )