The First Descendant

You will automatically obtain the parts for the Thunder Cage ultimate weapon during the story, but the crafting portion of this is an optional sub-quest similar to Bunny for The Sensible Life of Research (10G). Make sure you follow the steps once you get all four components to speak to Anais in Albion, then wait the four hours of research time (or speed it up with a consumable if you want), and then once you collect the weapon you will unlock this achievement.

Note: KEEP THIS WEAPON! You will need two copies of the same Ultimate weapon to unlock Growing Possibility (100G). Keep this in your inventory and then once you hit Mastery Rank 9, you can get a free second copy for that achievement.