Kumassacre

To obtain this achievement you must kill:
 * 10 Indolent Kumases
 * 10 Torpid Kumases
 * 10 Desert Lightning Kumases
 * 10 Patient Lithikumases
 * 10 Feytouched Lithikumases
 * Lagreah in Balder's Temple 5 times
 * Grig in Balder's Temple 5 times
 * Magnus in Balder's Temple 5 times

Tactics
Indolent Kumas and Torpid Kumas are found on Omphalos Plains in Celestial Hills.

Desert Lightning Kumases are found on Aurum Road.

Patient Lithikumases are found in Blessing Basin.

Feytouched Lithikumas are found in Seeliewood.

Named monsters are Balder's Temple bosses. Instant matching to Temple might not work since some bosses are optional and party usually skips those. However as Balder's Temple is level 60 content it's easy to solo it with current gear.