The Prism is the head of the Spectrum, the governing body of the Seven Satrapies, the emperor of the Chromerian Empire, and the worldly representative of Orholam. As such, he/she is part religious leader, part supreme government official, and part military general. In order to be named Prism, a drafter must a lightsplitter, meaning he can take white light and split it into all colors. He also has to be a full spectrum polychrome. This is necessary to become a Prism, but not to be a lightsplitter, as the Blinder’s Knife can somehow confer and retract this ability. It is stated in The Black Prism that only the Prism has the ability of lightsplitting. An additional ability that separates the Prism from all other drafters is that the Prism can draft an unlimited amount without the Luxin building up in his/her eyes.

The Prism is a religious figure in the religion that worships Orholam, and is the highest church official. He is to balance the magic to prevent bane from forming. This is done by expelling certain amounts of counteractive luxin whenever an opposite luxin because too numerous. For example, if the amount of Blue luxin were to become too great, the Prism would draft large quantities of Red luxin to balance the disorder.

The length of a Prism's term of service is always a multiple of seven: 7 years, 14 years, or 21 years. The one exception to this rule is in the cases in which a Prism has been assassinated or otherwise died while serving. According to Prism Gavin Guile, only four Prisms have made it to 21 years, and no Prism has served for longer than that.

The religious doctrine states that there is only one Prism born per generation. However this is not true as both Gavin and Dazen were Prisms, a reality which sparked the Prism's war. The Blinder's Knife can take the Prism's power away and it is alluded that it is used to make Prisms as well.

Although he/she is almost always referred to as "Prism" or "Lord Prism," the more formal titles of Emperor and High Luxlord also exist. The latter is because the members of the Spectrum (the seven Colors, the White, and the Black,) are known as Luxlords, and the Prism leads and rules them. Although the Prism is the emperor of the Seven Satrapies in title, the only time the Prism actually exercises his/her authority as emperor is when he/she is designated Promachos, which is only done during wartime or in a similar emergency situation.

Known Prisms include:

  • Lucidonius, who forged the empire of the Seven Satrapies, converted them all to worship of Orholam, established the Blackguard, and served as the first Prism.
  • Karris Atriel, later known as Karris Shadowblinder. Lucidonius' wife, member of the Blackguard, and the second Prism after her husband's death.
  • Sayid Talim (Held office for an unknown amount of time approximately 47 years before The Blinding Knife.)
  • Eirene Malargos, predecessor to Alexander Spreading Oak and namesake of the later Eirene Malargos, merchant queen and sister of Tisis. Ruled for 14 years.
  • Alexander Spreading Oak, Prism prior to the Guile brothers. A weak Prism who spent most of his time hiding in his apartments and was likely a poppy addict. Given that Gavin Guile became Prism at the age of 13 and his younger brother Dazen was alive for and remembered (albeit vaguely) Eirene Malargos' rule as Prism, it can be inferred that Alexander was Prism for only 7 years.
  • Gavin Guile, eldest Guile brother, elevated to Prism at the age of 13. When his brother Dazen was also revealed to be a Prism, it started a civil war.
  • Dazen Guile, masquerading as Gavin. Second Guile brother, actually won the War Of The Prisms, but decided to imprison his brother rather than kill him, and assumed Gavin's identity because most of his allies in the War were genocidal, psychotic, bloodthirsty, disreputable, or worse. Started losing his drafting abilities, one by one, after Zymun, his nephew, stabbed him with the Blidner's Knife after the Battle Of Garriston, on the orders of the Colour Prince.
  • Zymun, a full-spectrum polychrome and bastard son of (the real) Gavin and Karris White Oak- noble, Blackguard, and the current White- is currently being groomed to be Prism by his grandfather, Andross Guile. However, Kip Guile is also a full-spectrum polychrome, and the two half-brothers hate each other- Kip hating Zymun due to Zymun's wanton cruelty, history of serving the Colour Prince, and the role Zymun played in the massacre of Rekton, Kip's hometown. Zymun in turn hates Kip because he sees him as a threat to his power, status, and influence. It is therefore possible that there will be another power struggle for the Prismship or even another civil war.

The timeline of the following Prisms' terms of office has not been specified:

  • Leonidas Atrapos - Finer served during this Prism's term. Succeeded by Fiona Rathcore. May have served before or after Sayid Talim.
  • Fiona Rathcore - - Finer served during this Prism's term. Preceded by Leonidas Atrapos. May have served before or after Sayid Talim.