My feeling is that the best way to add "facts" in a way that makes your game more fun without limiting possibilities is to present the information in a format that is fallible - i.e. written sources, oral histories, first hand accounts of biased observers. This preserves the mystery of whether Arkat being raised by Aldryami really meant that he just came out of the woods, or grew up with powerful immortals, or was miscatalogued by foolproof Brithini methods, or that a magician did it.
Present it as in game information, from a Gloranthan's point of view. Unless of course, you're playing a game in which you are playing Arkat, just coming out of the woods, and about to begin your career as a 1st Level Fighter, with a +4 magic Unbreakable Sword.
Anything that happens in a game is obviously what *really* happened.
Keith