Doran spotted Joyeu saving a fishing boat from a sea serpent, which she took as prey. He met her again at Dragon's Nest, where Doran congratulates her on saving the boat, and she states that she hardly noticed the boat while hunting. Doran later learned from the Ralads that there were no more than two Ruby dragons left.
At some point after this, Doran sought Joyeu out again and convinced her to hide away and sleep until the king of Deltora woke her. She also promised him that she would not enter any other dragon's territory should she wake up first.
Lief, Barda and Jasmine searched out Joyeu after Fidelis, the dragon of the Topaz, refused to help them destroy the Sister of the East, due to it being in Ruby territory. It initially seemed that Joyeu had gone on a rampage, killing the guards accompanying the trio and the Capricon, Rolf, they saved. This dragon was later revealed to have been none other than Rolf, the Sister's guardian, in disguise. At the Dragon's Nest, the real Joyeu finally arrived, killing Rolf (once again in his dragon form). She then aided Lief in destroying the Sister of the East, freeing her land of the famine.
The Ruby dragon reappeared when Lief called her name to help destroy the grey tide. She killed the third Ak-Baba, snapping its neck between her jaws. Upon the tide's destruction, Joyeu remained in Del for a short time, during which she revealed why the Capricons' city, Capra, the remains of which Broome is built on, was destroyed. The Capricons had been stealing live Ruby dragon eggs, hollowing them out, and using them as lanterns. Despite repeated warnings by the dragons, the proud Capricons refused to stop, and the dragons destroyed the city. Lindal, who had assumed the Capricons were innocent victims, apologised on behalf of her people. Joyeu accepted and made a vow that so long as neither she nor her kin were harmed, she would never harm a human in Ruby territory. Joyeu was also present at Lief and Jasmine's wedding.
Like the other dragons, she has large wings and spikes in a row along her spine, and large talons and teeth. Her scales are a Ruby red colour, while her underbelly is pale and changes colour to match the colour of the sky.
Lief describes her as a "vast, glittering creature red as the setting sun, with eyes like glowing coals, wings like scarlet sails, and a tail sleek and slender as a stream of fire."
Joyeu has a very long tail ending with a sweeping "tuft" at the end, since Ruby dragons live near the coast, her spine is covered with webbed leathery flesh similar to that of sea serpents, possibly to enable her to swim.
Joyeu does not display many unique characteristics, but is loyal to her oath to Doran, like most of her fellow dragons. She seems to be fairly respectful and peace-loving, as she proposed the oath of peace she made with Lindal. Joyeu also seems to be relatively personable, actually staying in Topaz territory for a short time, though even she felt uncomfortable.
While a Ruby dragon seems to appear on the cover of Joyeu's debut novel, Dragon's Nest, it is in fact Rolf disguised as a dragon. Real Ruby dragons (along with all other dragons) have underbellies that match the colour of the sky and camouflage them during flight.
Joyeu's name is similar to "joyeux," a French word meaning "happy." The Ruby is also the symbol of happiness.