Patch 5.2 finally adds the Green Fire quest line for Warlocks. After finding a The Codex of Xerrath as a somewhat rare drop, you combine the tome with a Healthstone to bind it to you. If you want to test the quest line on the PTR, you can get it as a guaranteed drop from an NPC near the Shado-Pan Garrison.
10°
20°
40°
30°
40°
40°
Ad 
30°
