Ranger Lethvalin is a level 9 quest giver located at Tranquillien[45, 32] in the blood elf territory of Ghostlands.
After completing Help Ranger Valanna!, Ranger Lethvalin says,
"I received word that you were able to help Ranger Valanna and the lieutenant at Zeb'Sora.
Thank you, <class>. I suppose I should make my way back to Farstrider Enclave now."