Starfire is a Firemental Horse created by the Goblin Sorcerer Tangoo for Kara to bond with. Not only is he Kara's bonded, but also her paladin. Starfire was inspired by Moondance and Sunstar in Princess Gwenevere and the Jewel Riders.
Initially, it did not go well as the then unnamed Firemental stallion was impossibly wild and trusted no one. He broke free and escaped, leaving Kara to find the Blue Rose which would attract him to her. It worked, and Kara found that the stallion was torn by not having a real identity or a past, so she gave him her memories and named him Starfire. Together, the Blazing Star and Starfire went through elaborate tests to create magical elemental artifacts to attract a power crystal, and they succeeded. But as it turned out, the whole thing was a trap, set by the treacherous Tangoo.
Tangoo froze Kara's original bonded, Lyra, in quicksilver, which Kara thought was her fault, to motivate her into performing the tasks she would been assigned. Then once she would done so, he would steal the crystal and destroy Starfire as he would outlived his usefulness. But what he did not count on was Kara and Starfire's combined power attracting a second power crystal. With the help of her friends on Earth and Aldenmor, and the Goblin Prince Lorren and his friend Tasha, Tangoo was thwarted and banished to the Otherworlds. Duty done, Starfire vanished, promising to always be by Kara's side spiritually.