Demon Ruins
Once you have reached the Demon Ruins bonfire, you should have picked up the Shield of Want near the Carthus Sand Worm. The most dangerous enemies in Smouldering Lake are the Smouldering Ghrus who wield fire orbs, the jumpy Ghrus, and the Black Knights. You now should have a +6 main weapon and a +6 offhand weapon. If not, use the Ghrus to farm (Large) Titanite Shards. While 2-handing a Raw infused Claymore+6, 2 hits with R1 are sufficient to stagger a Smouldering Ghru who wields a fire orb and 7 hits with R1 are enough to kill it. Each regular Ghru can be easily dispatched of in 3 hits with R1. A jumpy Ghru can grab you and buff itself; be sure to kill it as quickly as possible. An effective way to deal with a jumpy Ghru is to use a weapon having a vertical (possibly 2-handed) R1 swing. Any Black Knight is very strong and dangerous; only one R1 and move or roll away. If you want, lure a Black Knight to a bunch of enemies and let the Black Knight farm souls for you.
Starting from the Demon Ruins bonfire, head down the staircase and kill the Smouldering Ghru who wields a fire orb. Proceed along a hallway and kill 4 Ghrus. Turn left into a room with 2 jumpy Ghrus; kill them and ignore the Smouldering Rotten Flesh hanging on the ceiling and the Demon Statue. Jump down through a hole in the floor to a lower level and kill 3 nearby Ghrus. Head to an adjacent room to kill 2 Demon Statues and 3 Ghrus. Enter the room blocked by an illusory wall, wait for the Black Knight to kill the Ghru, and then kill the Black Knight. Make your way to the Old King's Antechamber bonfire, kill the nearby Smouldering Ghru and 3 regular Ghrus. Equipping only the Silver Serpent Ring+0 and the Shield of Want, each round yields approximately 8,304 souls. If you also equip the Symbol of Avarice, each round would earn you approximately 12,470 souls.
Farming souls: Demon Ruins, Dark Souls III
Below are some data on the approximate amounts of souls you would obtain if you use the above route for soul farming in various NG cycles. The data were gathered while equipping the Silver Serpent Ring+3, Symbol of Avarice, and Shield of Want.
- NG+0: 15,304