Ryathen the Somber at Falcon Watch in Hellfire Peninsula wants you to bring him 6 Felblood Samples from the Terrorfiends that inhabit the Pools of Aggonar.
Northeast of here lie the Pools of Aggonar. Once a sacred site to the draenei, their waters were corrupted after the blood from the demon Aggonar was spilled into them.
That blood, though old and diluted, still possesses tremendous power. Terrorfiends now walk the area, empowered by the pure demonic energies of the original blood. Slay them and retrieve as much felblood as you can. I'll make it worth your while.