The term penitent refers to fallen angels who decided to avoid conflict among other angels and live humbly among humans instead.
Background[]
The penitents were led by the angel Rebecca. Because of their avoidance of armed conflict, penitents gained the support of other angels. However, this also caught the attention of other factions who wanted complete control. Bartholomew's angels launched an all out offensive against the penitents, ultimately wiping them out.
Legacy[]
Although Elijah, one of the last members of the original penitents, was killed by Bartholomew, Bartholomew himself was killed by Castiel, who shared a similar belief with the penitents. After leaving the camp of Bartholomew's angels, Castiel later visited Rebecca's grave. He was then followed by angels who previously served Naomi's protege, one of whom offered his service and loyalty. Whether or not they would also call themselves penitents is unknown.