HOMEWORLD: Erde-Tyrene (Earth)
BORN: c. 97,445 BCE
343 Guilty Spark started life as the human Chakas on Erde-Tyrene, now known as Earth. Chakas' experience with the Ur-Didact and IsoDidact eventually led to his mind being uploaded into the carapace of a Forerunner monitor, initially called Monitor Chakas, then 343 Guilty Spark. Guilty Spark was assigned to Installation 04, which he served on for nearly 100,000 years until its destruction at the Battle of Installation 04. After the Halo's destruction, he was captured by the Covenant, who led him to Installation 05 and later the Ark. Guilty Spark was instrumental in helping John-117 and the Arbiter defeat the Covenant at Installation 00, though he turned on the UNSC forces, killing Sergeant Johnson.
Guilty Spark was rediscovered by the UNSC Rubicon on Installation 00 in 2554, where he stole the ship and left the Installation for his own purposes. Three years later, Spark, with the memories of Chakas reawakened within him, was found by a salvaging crew led by Rion Forge and made a part of the crew of the Ace of Spades, helping in the hunt for the UNSC Spirit of Fire.