The Oath Flame has the characteristics of both the Sky and Earth Flame, Harmony and Gravity Manipulation. It was created when the Earth Simon Ring and the Ring of the Sky Version X fused together. Tsunayoshi Sawada used the Earth Flame's gravity ability to wrap his shattered bones back together, creating a reinforced skeleton. Tsuna can also use the Earth Flame's Gravity Manipulation to slow down or even immobilize his opponent, although it can be countered if the opponent cloaks their body in the Flame of Night, as shown in Tsuna's battle versus Demon 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.