Fyrnocks, beings based on silicon, were originally from the jungles on the planet of Anaxes. After their homeworld was destroyed, numerous fyrnocks took up residence in the resulting Anaxes asteroid belt, notably on the asteroid known as PM-1203. This asteroid housed Fort Anaxes, a military installation utilized by the Grand Army of the Republic during the Clone Wars. Sunlight was harmful to fyrnocks, restricting their existence to darkness, where they transformed into formidable predators. However, they possessed immunity to non-solar light sources.
Fyrnocks were a dangerous silicon-based species that used sharp teeth and claws to attack their prey. Asteroids were ideal habitats for fyrnocks. While typically the size of a small humanoid, some fyrnocks were known to reach significantly larger sizes.
A particular fyrnock stood out for its immense size, dwarfing the typical fyrnock. This creature was significantly more dangerous and was, in fact, the mother of all fyrnocks. Years following the Clone Wars, the Jedi Padawan Ezra Bridger called upon this fyrnock, but he had to draw power from the dark side to accomplish this. The fyrnock engaged in a fierce battle with the Grand Inquisitor, providing Ezra and Kanan Jarrus with the time they needed to escape. However, Ezra was briefly rendered unconscious and left shivering due to the unexpected strength of the dark side energy he had used.
During the Battle of Anaxes, fyrnocks were observed lurking near a campfire established by Clone Force 99, CT-7567 "Rex," CC-2224 "Cody," CT-5597 "Jesse," and CT-6116 "Kix." Several years after the Clone Wars and the destruction of Anaxes, Hera Syndulla and Sabine Wren encountered fyrnocks within the confines of the abandoned Fort Anaxes. Later on, Jedi Knight Kanan Jarrus and his apprentice Ezra Bridger made their way back to Fort Anaxes, with the intention of drawing the Grand Inquisitor into a trap. Through the Force, they managed to persuade the fyrnocks to launch an assault on the Inquisitor and his Imperial stormtroopers. Despite their inability to ultimately defeat the Inquisitor, the fyrnocks succeeded in eliminating a number of stormtroopers.
The initial appearance of fyrnocks occurred in the Star Wars Rebels episode titled "Out of Darkness." According to the episode's guide, they were originally intended to be called garcors, and subsequently nockfyrs, reminiscent of bats. Dave Filoni, the series' executive producer, proposed reversing the syllables of the name to arrive at "fyrnock."
The episode guide for "Gathering Forces" strongly suggests that the powerful fyrnock summoned by Ezra is, in fact, the mother of its species. This information was confirmed in the title Ezra's Duel with Danger.