Files are Forgotten Artificing Profession Assets that can be acquired as necessary components for completion of a number of rare Forgotten Artificing tasks (levels 14-20) and/or as optional components that will improve the chances of increasing the quality (Tier) of finished Forgotten Artificing tasks.
A [Worn File] may be purchased for 1 from M'tari Prin'tal in Protector's Enclave (North corner of the Seven Suns Coster Market). Files of higher tiers may be acquired from [Professions Booster Pack] and asset packs purchased in the Zen store. Files are not bound and may be traded on the Tarmalune Auction House or transferred between players.
A task requiring a File as an asset will take any tier of File in its slot. Higher tiered Files serve only to improve the chances of producing a higher tiered result in rare tasks for which they are used.
At Profession Level 3, 4x [Iron File] can be upgraded to produce a [Steel File].
At Profession Level 4, 4x [Steel File] can be upgraded to produce a [Mithral File].
There is no task that will allow a [Worn File] to become an [Iron File].