This is what is called Priori Incantatem. Priori Incantatem is a magical phenomenon that can happen when 2 wands that share the same core are forced to complete in combat. It is called the " Reverse-Spell Effect." In the middle when the 2 wands connect it turns in to a gold color and sometimes people come out of one of their wands to help the other person win the duel. It is AMAZING!!