The Dragonfires were a barrier against invasion from the Planes of Oblivion that were created from the blood of Akatosh and given to Saint Alessia. The lighting of the Dragonfires was a ritual devised by Reman Cyrodiil to accompany the coronation of a new Emperor. The fires were relit whenever an heir ascended to the Ruby Throne. They were kept burning throughout his or her lifetime and represented the Covenant between the Cyrodiilic Empire and Akatosh. According to legend, they protected Nirn from Oblivion. The pedestal that served as a pyre may be found in the Temple of the One in the Imperial City, though there seems to have been no apparent connection between the ritual and the Alessian teachings. An Emperor had to use the Amulet of Kings to light the Dragonfires.
The darkening of the Dragonfires played an essential role in Mehrunes Dagon's invasion of Tamriel in 3E 433; when the Dragonfires were not lit, Mundus was again vulnerable to invasion from Oblivion. With the assassination of Emperor Uriel Septim VII and all of his legitimate heirs by the Mythic Dawn cult, the barriers between Oblivion and Mundus were broken, allowing stable portals to the Deadlands to be created. When Martin Septim smashed the Amulet of Kings to summon an avatar of Akatosh, the barriers were resealed permanently, thus ending the long but now obsolete tradition.