The weapon could be purchased by any participant at the Item Shop in the events of the Development Match of the Workshop Battle, as long as the participant possess enough points to purchase it. Because of Yeon Yihwa suggestion during the events of the Workshop Battle, Rak decided to purchase it.
Mad Shocker is a throwing spear  that changes shape as it is thrown and has a higher destructive power than a normal spear. It is likely to be at least an E-rank weapon considering his current level. Despite Mad Shocker being designed to be a throwing spear, the item is good for both offence and defence.