Ink Stone is the strongest mount in the Power category for horses. Its other name is Three Kingdoms Black (三国黒, Mikuni Guro), the horse that Tadakatsu rode at Battle of Sekigahara.
It was a personal gift from Ieyasu and said to have been approximately nine feet tall. Tadakatsu rode the mount when he tried to pursue Mitsunari's momentary withdraw from the battle front. By the time he caught up with Mitsunari's resting men, he met Yoshihiro's determined force. With the Shimazu intent on plowing through the Eastern army, Tadakatsu had come close to injury when Three Kingdoms Black was shot by their rifles. Although Tadakatsu toppled from his dying mount, he amazingly recovered from the fall and his vassal, Oda Nobuteru, provided him another horse for his chase. Three Kingdoms Black died of its wounds that day, but it continues to be mentioned in his rider's heroics at Sekigahara.