Keilus was Jiralhanae that, while born into the Jiralhanae Alliance's society alongside his twin brother Ulorus, chose to join the Covenant Remnants and fight against the United Sangheili Republic and its' allies, eventually rising to the rank of Chieftain. However, after the deadly blood-bath of Operation: FIRE and its' subsidiary operations, Keilus was taken back to the Alliance by his brother, where he would be nursed back to health and go on to fight alongside his brother in the Lance of Unrelenting Reparation.