When Flame Princess is exposed to extreme romance, her Elemental Matrix will become unstable, and she will burn so hot that she will melt down through the Earth's crust. Then she will be thrown by gravity back and forth until she burns the world from inside. In "Burning Low," Finn kissed her, thus making her elemental matrix become unstable. However, the process was stopped because of the lack of oxygen, and Flame Princess was burned out before she could burn the whole world. However, this may be not a power but a condition or disorder, since Flame Princess does not manipulate it or permit it to happen.In "Earth & Water," it is mentioned by Princess Bubblegum that Flame Princess's elemental matrix stability is somehow connected to her feelings.
The exact length of the spell is unknown but Jake has the protection for most of the episode. It seems that the protection disables itself when not around fire or intense heat. However, exactly what causes it to disable is not clear because Jake is blue up until he goes into the Tree Fort. The spell wears off when the lighting changes, directing attention away from the Flame Shield's protection ending. However, in "The Red Throne," Cinnamon Bun is under this spell for the whole episode, even when he is outside the Fire Kingdom, suggesting that it can last for a long time and making the reason of disabling a mystery. It seems to be cast by using a chant that involves different hand gestures and arm movements as it is said. As he chants, Flambo also creates a series of runic symbols. He spits on Jake once the spell is cast, but that was apparently just to spit on him.
In "Ignition Point," Flambo uses it again, this time on both Finn and Jake. He did the same spell, then punched them on their foreheads.Cinnamon Bun can also be seen under the spell possession in "Earth & Water." It is likely Flame Princess who cast such spell on him.
Flame SwordFlame Sword is an ability of the Flame Princess, first used in the episode "Vault of Bones." It appears as intense, isolated, bright blue-and-white flame. It has the appearance and sound of the flame of an oxy-fuel torch. She uses it to cut through a metal door in the Vault of Bones.
Heat Sense is a power also displayed by Flame Princess, first shown in "Vault of Bones." The ability is used by Flame Princess in the episode to detect something out of place, which turns out to be a fake tree. She uses the ability after Finn is unable to find a secret switch for a dungeon. Flame Princess uses this ability by spinning around in place and sending out heat waves. This ability does not burn anything the Heat Sense is in range to.
This ability may work like thermal imaging, where sending out infrared energy (via heat rings), and seeing how it reflects off of objects. Another theory is detecting how flammable the various materials are in the detection area, as different molecular compounds and structures have different ignition points.
Scatter Fire is an ability in which she emits four manipulable bolts of fire. Scatter Fire was first seen in "Vault of Bones" when Flame Princess defends herself against a skeleton that wanted her to "take its place."
Flame Princess also has a snake fire ability, in which she can send flames up strands of anything. Flame Princess first uses this ability in "Vault of Bones," when she defends herself against the Goo Skulls.
Seen briefly in "Frost & Fire," Flame Princess shoots a huge beam of fire at the Ice King, who also also shoots ice at her. When the two beams meet they create a huge explosion.
Flame Lord demonstrated two types of flame spells in "The Red Throne." Both of these spells are cast with chants, which utilizes different colors of flames to send out heat waves towards another being or object. The first spell used is cast with green flames, and it can control people's minds to follow commands of the user. However, when the user is knocked out, the spell is cancelled out due to the caster's distraction. Memories while brainwashed will not be removed from the victim after the spell has ended. The second spell is cast with blue flames, and its ability is to remove and destroy other items.