Firecats are assigned (presumably by Vkandis) to accompany a human, usually to designate a new Son of the Sun, and to advise the Son of the Sun as a direct representative of the sun god. Firecats will also accompany and advise individuals whom Vkandis believes to be figures who are likely to be central in coming events that the Sunlord wishes to influence.
The first one or two were created by Vkandis, but the ones after that are the reincarnated forms of previous true Sons of the Sun and others Vkandis deems worthy. In this way they are similar to the Companions in that they are returned spirits. Because there are far fewer Sons of the Sun than there are Heralds, there are far fewer Firecats than Companions. Firecats do not make any attempt to hide their reincarnated nature, and use the name they were known as when they were Son of the Sun.
They resemble Siamese cats the way that Companions resemble horses, except that they are much larger, and have cream-colored fur with brick-red tail, ears, and mask around blue eyes. Though they may like to pretend otherwise, Firecats are mortal.
Firecats have several special abilities. They can protect themselves and others magically, usually by setting their attacker on fire, and can travel long distances by a method known as 'jumping,' which is a form of Fetching. They can bring people and objects with them using this method, though people tend to feel sick after this, which usually manifests as headaches. The extra "load" is also very tiring for the Firecat. Two Firecats working together can also create a Gate. In "present day" Velgarth, there are two prominent Firecats. One is Hansa, who guides Solaris, the current Son of the Sun, and the other is Altra, who guides Karal, Sunpriest and current Karsite ambassador to Valdemar.
Altra specifically states that he and the Companion Florian are mages. (Storm Warning, Chapter Sixteen) It is not made clear if all Firecats and Companions are mages, or if all have some mage abilities, but only some individuals are true mages. This could be rather like Mindspeech among Heralds. Nearly all Heralds can Mindspeak their Companion, but only a few are true Mindspeakers with the corresponding increase in abilities.