The True Fire Rune is one of the 27 True Runes, representing the power of fire. The Fire Rune and Rage Rune are born from this True Rune. It is currently owned by the new flame champion, but it used to be owned by Harmonia. Hidden in the depths of the One Temple, this rune was stolen by the "Fire Bringer." Since then, the "Flame Champion" fought against Harmonian troops and even defeated them in numerous battles. However, the Flame Champion disappeared after wishing to be free from the True Rune's destiny, removing it from his body using an ancient Sindar secret. However doing so caused the rune to go berserk and start a fire storm that last for 10 days and 10 nights. Both the Grassland army and Harmonia's regular army were all but wiped out. Soon after the rune was sealed away in the Flame Champion Hideaway.
However in SY 475 the son of the Karaya Clan chief, a young Karayan named Hugo ventured to the Flame Champion's Hideaway in the hopes of protecting grassland. After discovering the truth about the Flame Champion, Hugo decided to bear the True Fire Rune himself. While the rune was able to help Grassland repel the advancing Harmonian army and united Zexen and Grassland it was eventually stolen by Luc at the battle of Brass Castle. Soon after though the Fire Bringer advanced on the Ritual Site where Luc and his party were preparing to destroy the 5 elemental true runes in the hopes that it would crush Luc's soul and finally bring him to peace. However the True Fire Rune as well as the other 3 stolen True Runes were recovered and Luc was defeated finally getting his wish of being able to die.
- Blazing Wall: Deals 400 damage to target + foes and allies in area.
- Explosion: Deals 700 damage to target + foes and allies in area.
- Final Flame: Deals 1200 damage to a single foe.
- Hellfire: Deals 1500 damage to target + foes and allies in area.
- Along with the Soul Eater, this rune does the second most direct damage to enemies in the series, with the first being the True Lightning Rune.