As soon as you reach level elemental 19, go in Anemos during the night and help the other players to spawn and defeat Pazuzu, the Monster that rewards three Feathers for eliminating it.
I seem to be getting the benefits of this long ordeal but the completed 9th book never vanishes leaving me with the uneasy feeling that something was not completed properly.
Not only do they get big and do more damage, but they can change element too.
After Cloud of Locusts, Pazuzu will usually cast either Gale Cannon or Plague of Locust.
Each Anemos Crystal can be exchanged into 2 - 5 Protean Crystals by luck.
Or you need help in any step of the relic weapon? She's a green little fellow that looks like the Anima fairy in Heavensward.
I heard Pyros is more fun and I'm glad I'm breezing through pagos.
If all you care about is the Relic, then these are totally skippable.