WHERE TO FARM IT
Which area you farm is decided by the area's monster level, not by the item — the rule is the same for everything, so it lives on the mechanics page.
NAMED TARGETS
Named monsters that can be farmed deliberately. The list spans all three difficulties; each monster appears once, at its most rewarding one. The figure is an estimated average kill count.
Duriel
normal · Lv 22
~1 every 13 kills
Coldcrow
normal · Lv 4
~1 every 14 kills
Bishibosh
normal · Lv 2
~1 every 14 kills
Bonebreaker
normal · Lv 2
~1 every 14 kills
Corpsefire
normal · Lv 1
~1 every 14 kills
Andariel
normal · Lv 12
~1 every 17 kills