Pure White Feather - 5G
This achievement is only unlockable if you own the Wings of the Goddess expansion.
Description: Obtained the key item "pure white feather."
How to get it: With Wings of the Goddess installed, travel to Battalia Downs grid H-5, Rolanberry Fields grid H-6, or Sauromugue Champaign grid K-9. Somewhere in those grids you will see a large statue/ root that looks like a mouth (hence the name MAW). Talking to it will activate a five-ten minute cut scene. During this cutscene you see yourself sucked into the Maw, and a bunch of Chocobo Riders will see you and tell you to travel to the Necropolis.
Blah Blah Blah, and at the end of the video you'll have the pure white feather. The feather allows you to get back out of the "past". Talk to the Maw you appear in front of to warp back to the present. You may not return to the same Maw you left in, so be prepared for a bit of a walk just in case.
When you're back in the present, talk to your achievement bard to unlock this.