Flame Princess's Elemental Matrix

When Flame Princess is exposed to extreme romance, her Elemental Matrix will became unstable and she will burn so hot and melt down through the Earth's crust and then burn the world from inside. In "Burning Low", Finn kissed her thus making her Elemental Matrix to become unstable. However, the process was failed because lack of Oxygen and Flame Princess was burned out before she could burn the whole world.

Trivia

 * This explains the reason why Flame Princess was locked inside a jar in "Incendium".
 * In "Burning Low", Princess Bubblegum stated that she already told about Flame Princess's elemental matrix to Flame King.
 * Princess Bubblegum is the first to know what will happen to Flame Princess's elemental matrix if exposed to extreme romance.