Fly to Sparktouched Haven, southwest of Rainspeaker Canopy, and just to the west of the Mosslight Pillar, and kill Frenzyhearts aorund Kartak's Hold (24,80) until one of them drops a Tainted Crystal. It has a very high drop percentage. Once you've got the crystal, take it to the Great Lightning Stone (33.7,75), and activate it. This will transform you into Soo-holu, a spirit beast which fights like a cross between a rogue, feral druid, and DPS warrior.
You don't actually have to take control of Soo-holu to complete the quest. Since you can't loot kills while transformed and you don't need to be transformed to get credit, you may want to just kill them so you won't miss out on the loot.
You may want run to Kartak's Hold, rather than trying to pick off the raiders attacking Sparktouched Haven. It's the Frenzyheart village just to the southwest. Just be careful not to let yourself get overwhelmed. The respawn rate is very high and there are lots of them.
Turn in the quest to Lightningcaller Soo-met (33,74) when done.