Gather 10 Drinial glint stones from around the Direwolf Warrens. They spawn around ( 292, -56, -193 ) /waypoint 292, -56, -193.
Return to Drizas N'Ryt and he will give you 10 Sunflash Stones. NOTE: The Stones are NO ZONE, if you exit Darklight Wood (for Moonlight Enchantments, for example) the stones will disappear - run back to Drizas and ask for more and he'll give you five for each request you make.
Head to the T'Rethir Vampire area where you'll need to examine and release a Sunflash Stone near a random number of T'Rethir priests. You'll have to release the stone, then kill the T'Rethir Vampires ( DO NOT have to be Priests ). They spawn around ( -241, 6, -313 ) /waypoint -241, 6, -313. There generally will not be enough priests amongst the other mobs to do this part without waiting for respawns. Do NOT however (despite the boredom if high level) camp to an alt, as you will lose the Sunflash Stone.