I'm going to answer the question I think you meant to ask since I have never, ever heard of "Fie"
I think the TLA you are after is "KEI"?
This is what people are perpetually shouting to zone "Anyone giving KEI?", "Any KEI about?" etc, etc
If I have guessed right and win the cookie then it is Koadic's Endless Intellect a mana regeneration spell for levels 45+ which means your mana comes back faster so you can cast more, kill faster, heal more. It is highly addictive and should only be taken under supervision.
Of course if I guessed wrong then I'd like to know what "fie" is too
. Also who wants it and how much they're willing to pay.
Afterthought - was it a halfling with a lisp?
If so then they are looking for "pie" which is the goal of all halflings everywhere and is most easily bought in Neriak where halflings are made most welcome.