|This article is about a/an ally in Power Rangers Mystic Force.|
- ―Fire Heart's first words after being born[src]
Fire Heart is a dragon born from the last remaining dragon egg in existence.
At some point during or after the great war between good and evil, an unknown party sealed the egg in a puzzle chest and hid it away in Mt. Fuego, alongside a monster to guard it. They hid the scroll showing its location in the depths of the Cimmerian Forest, and the map showing the way to the scroll's location became lost to history, as was the truth of the chest's contents; the only thing known of the Fire Heart at the time the series began was that the ancients believed that it was a source of tremendous power.
Finding the Map
Archaeologists eventually located the map, and planned to examine its meaning at a museum. Necrolai learned of it, and sent the Taxi Cab Monster to steal the scroll. It met Necrolai in the parking garage to hand it off, and the rangers arrived shortly afterwards. Thanks to the garage's surveillance footage, they gained a copy of the map and Udonna deciphered it. The Rangers raced Necrolai through the forest, locating the scroll that showed the secret of the Fire Heart before Necrolai arrived. After a struggle, they accidentally tore the scroll in two, and Necrolai and the Rangers each escaped with half of the map.
The Treasure in the Mountains
For a time, both parties tried to decipher their halves of the scroll, to no avail. Chip found the answer when he saw Xander staring in the mirror, reasoning that the two halves of the scroll were mirror images, and putting the scroll next to a mirror, they recognized Mt. Fuego. Leelee overheard Chip's epiphany, and passed the news on to her mother. The Rangers located the Fire Heart, destroyed its guardian, and fended off attacks from a Styxoid and its army of Hidiacs that Necrolai sent to retrieve the chest. However, a one-hour timer started on the box when the rangers removed a scroll, which stated that if they couldn't solve the puzzle before the timer ran out, the Fire Heart would be lost forever. The rangers exhausted nearly half of the time trying to solve it themselves, then Chip decided to pass the chest over to their boss, Toby, who they knew to be an expert at solving puzzles. Fortunately for them, Chip's faith was well-founded; with seconds to spare, Toby determined which button on the chest will unlock it. Vida pressed the button with only one second to spare, and the chest opens. The Rangers thanked Toby and returned to Root Core, Xander distracting Toby from wanting to learn of the chest's contents by telling him a riddle. Udonna identified the contents of the chest as the last dragon egg.
Dealing with a Dragon
The Dragon Egg continued to grow for some time, until it finally reached the point where it was ready to hatch. While a Dragon book said to just crack the egg open with a hammer, Clare would not have that happen. Jenji then instructed her to sit on the egg and wait for it to hatch. Sure enough, the egg did hatch and the dragon appeared, calling Clare its mama.
The Rangers soon became very interested in little Fire Heart. So much so, that Jenji became jealous of the dragon. The genie took Fire Heart and left him out in the forest to survive alone. After learning of this, the Rangers and Jenji went back to find Fire Heart, but he was nowhere to be found. What they didn't know was Phineas had found the baby dragon and taken him in and given him the name PJ (for Phineas Junior). The little Fire Heart then dubbed Phineas as his Daddy.
When Phineas awoke from a nap, he was then surprised to find Fire Heart had left him. It was then that both Clare and Phineas discovered they were looking for the same dragon, and Fire Heart then showed himself, having grown to his full size.
He later helped the Rangers by flying Solaris Knight to the city, when he needed to save Jenji. He was also capable to transporting the Rangers to other dimensions, as he did when the Dark Wish was active.
In time, Fire Heart would prove to have a great deal more powers and abilities.
After months of care and training, Fire Heart's true destiny finally came to pass. When he and the Red Ranger joined together, they formed the Red Dragon Fire Ranger.
Having heard reports of a magical dragon just outside Briarwood, Andrew Hartford went to Toby Slambrook's Rock Porium and purchased one of Fire Heart's scales, which he used to power the Defender Vest that would be used by his Overdrive Rangers.