Windstorm Box
Double-click to obtain one of the following items: Dandy's Home Run Ball, Dandy's Golden Ball, Ruler's Authority (7-day), Nevit's Cloak of Light (30-day), Emperor's Rune Pack (2-hour), Bloody Weapon Upgrade Stone, Dark Weapon Upgrade Stone.
Not dropped by monsters.
Cannot be spoiled.
The chances are official (x1). On servers with x10, x100 and higher rates, drop and spoil come more often.