Killing all the Knights in one go will reward you approx 60000 Souls.
There are 2 mechanics that I know of and. Take them one by one as their attacks are very heavy and destructive, but each Winged Knight will reward you 17000 Souls and more so definitely this is the fastest and easy Souls Farming Location in Dark Souls 3. Im kinda new to dark souls III (I am now in catacombs of carthus) but I do know a lot about dark souls mechanics. Once you come out take the left stairs and from the rooftop you can see 3 Winged Knights. The Final Farming area is from the Grand Archives Bonfire take the left elevator and head up. Also, you need to take down the Havel of the area first or else he can be summoned. Here you don’t need a reset the area but remember there is no loot drop it’s just for Soul farming. Simply stand behind the Summoning Sign and once the enemy is summoned give them the best backstab and repeat the same.
Fast travel to the Dragon-kin Mausoleum Bonfire then head inside you see the summoning sign where you get 5200 Souls for each kill.
This is one of the best places to farm Souls without losing a single health if you know how to backstab properly.