Elune's Blessing

Get the quest from Valadar Starsong he is at 53, 35 in Moonglade. The quest can be shared.

Summon Omen around 65, 58

Note that you don't need to have killed Omen yourself to complete the quest, after he is dead there will be a beacon of light on him, stand in the beacon and the quest will complete.

Please note that if you do intend to kill Omen, you will need a raid group, 10-15 is usually sufficient, with a couple of healers and you WILL need a tank of some sorts. His overall damage isn't too bad, but he does use a starfall AoE attack occasionally. He has 5.5 million health.

Your reward for completing the quest is Elune's Lattern which makes an Elune Stone with a 24 hour cooldown. You'll also receive a ton of fireworks, and of course, 10 achievement points.

Good hunting!

To summon Omen you must throw rocket clusters into both the cluster launchers at the same time.

You dont really need to kill Omen.
I joined a raid to kill him once, but a Horde raid was before us. When they were done, we found out you could just walk under the light on Omens corpse, and you will recive Elunes Blessing.