Edge is the rune word 'TirTalAmn' for missile weapons in Diablo II: Lord of Destruction. Edge is a reasonably cheap weapon that grants decent bonuses, but above all it offers the extremely rare "reduce all vendor prices" attributes. Since it has no competition with any weapons in that category (the only other item that offers the mod is a charm), it is always useful to keep in stash for any character that would visit NPC shops for any reason.