Plague Idol

What drops it

 * Am Fah Marksman
 * Am Fah Assassin
 * Am Fah Healer
 * Am Fah Necromancer

Locations

 * Wajjun Bazaar
 * Unless you are currently friendly with the Am Fah (see Seek out Brother Tosai, this is a great farming location. From The Marketplace, follow the eastern edge of the area south to The Undercity, then head east to Nahpui Quarter. Rezone and head back the same way.
 * Note that while there are a lot more Am Fah in the zone, this is the most efficient route in terms of reducing time spent walking to/from portals or between groups of foes.


 * Nahpui Quarter (explorable) and Shenzun Tunnels
 * Start from Senji's Corner, clear out the Am Fah infesting the underside of Nahpui (don't bother going up the ramp, the upper levels only contain Jade Brotherhood), then continue on through the tunnels.


 * Sunjiang District (explorable)
 * Make a round-trip between Zin Ku Corridor and the Pongmei Valley portal.


 * Deactivating P.O.X.
 * This mini-mission starts with a battle against a very large contingent of Am Fah.


 * Cantha Courier Crisis
 * This easily-farmed solo quest is packed with both Am Fah and Jade Brotherhood, making it ideal for farming both Plague Idols and Jade Bracelets at the same time.

Tactics

 * The Am Fah in Wajjun Bazaar and The Undercity usually appear in groups of 4. Watch out for patrol patterns that put 2-3 groups together. In the UC and often in the Bazaar, the groups will include a Monk, a Ranger, a Necromancer, and an Assassin. For most teams (and soloists), the Am Fah Healers will present the most serious obstacle; they are relatively efficient keeping their team alive (compared to how quickly the other 3 can hurt your team).