Ernoul himself is mentioned only once in history, and only in his own chronicle. He was a squire of Balian of Ibelin, an important crusader noble in Jerusalem, and accompanied his lord on an embassy from King Guy of Jerusalem to Count Raymond III of Tripoli in 1187. Balian and his retinue remained behind for a day at Nablus during the voyage to Tripoli; the rest were ambushed at the Battle of Cresson on May 1. It was Ernoul who investigated the almost-empty Templar castle of La Fève before news of the battle reached Balian. No other mention is made of Ernoul. However, it is clear that he was at the Battle of Hattin on July 4, as his chronicle gives an account from the rearguard, which was commanded by his master Balian.