The Temporal Stone is one third of the Chrono Cypher, an ancient magical device created to allow the wielder to see every possible version of the past, present, and future.
The 700-carat colorless diamond was forged and cut by legendary stonecutter Er Starblood and imbued by Master Thaumaturge Harun Aetherium during The Evanescence in the 3rd Century of the Telos Era.
Starblood and Aetherium forged the stone in secret because it was against the law to use magic to view or manipulate spacetime out of fear of how that power could be used.
The Temporal Stone was first discovered by the Babylonian King Hammurabi who used it to develop the Code of Hammurabi and the conquest of Mesopotamia.
It then passed hands several times throughout history before eventually ending up in the hands of the Syndicate after its agents stole it from the Library of Alexandria before helping Roman Emperor Aurelian sack the city, and destroy the library, in 272 AD.