Lod Mron, better known as the Prophet of Regret, was born in 2461 on High Charity. He was initially the Vice Minister of Tranquility before eventually rising to the rank of high prophet along with the Prophet of Truth and the Prophet of Mercy. The high prophets were instrumental in starting the war with humanity in 2525, and continued to push for their destruction through the following decades. Regret had a tendency of being more involved with combat operations than the other prophets, and as such, developed an affinity for the Sangheili and their culture.
He led the initial attack on Earth in 2552, though he and his fleet were unaware Earth was humanity’s homeworld until they arrived, instead looking for the Portal at Voi. When faced with potential destruction, Regret and his carrier escaped Earth via slipspace, jumping to what was determined to be Delta Halo. Regret and his forces deployed to the surface of Installation 05, though he was killed by John-117 just prior to the Prophet of Truth initiating the Great Schism.
Though Regret was killed, the Gravemind captured Regret’s body and managed to reanimate him, using his knowledge to determine the location of the portal to the Ark. Regret continued as an assimilated part of the Flood until the activation of Installation 08 at the end of the Battle of Installation 00.