A yaga, which was conducted by kings to rid themselves of harm. The king would send a horse with a plaque on its forehead to travel as per its wont, and would fight anyone anyone who stopped it. Any king who could complete hundred ashwamedha yagas was eligible to become an Indra. (This yaga was usually conducted by emperors who were all powerful. As per the vedas, the horse would be accompanied by a hundred kshatriya warriors)