The Oath Flame is a combination of the Earth Flame and Sky Flame that forms an extremely powerful Flame. This Flame has the abilities of both the Sky and Earth Flame and was created when the Earth Simon Ring and the Ring of the Sky Version X fused together. Tsuna used the Earth Flame's gravity ability to wrap his shattered bones back together, creating a reinforced skeleton. The user can also use the Earth Flame's Gravity Manipulation to slow down or even immobilize his or her opponent, although it can be countered if the opponent cloaks their body in the Flame of Night, as shown in Tsuna's battle versus Daemon Spade. Using the Oath Flame, Tsuna is able to fire the X-Burner without having to take time to balance the Flames. Tsuna's use of this Flame is possible because of his Sky Flame's Harmony and his own ability of understanding the other Flames.