Heartless (Black Cloak)

"We protect the Underworld, defend the realm of men and serve the Great Lords and Ladies of the Underworld. Our pacts last for our life. Only death may relieve a black cloak of his duty"

- Lord Rhaegar Heartless famously known as "Black Cloak" is a organization in the Underworld that appears in DxD Black Lamb made up of hundreds of powerful and trained devils in the Underworld. Typically made up of devils from noble families who won't inherit clans when their parents decide and want to make fame in a different way. Heartless is the complete opposite of the Underworld's Kingsguard, with the Kingsguard serving the Great Satans but Heartless serving the remaining families of the 72 Pillars, typically working as a police force and even working as private detectives, having jurisdiction to work on cases in the Underworld, Demon World, and on Earth.

Similar to the Kingsguard, there is a ranking system similar to that of a human world army, however in that ranking system there are two classes of members either called "Knights" or "Detectives" there is shown to be no difference in the power or influence a member of either class possesses, knights just refers to members who work in the Underworld typically as police officers or as guards in most cases and detectives refers to members who can work either outside or inside the Underworld as investigators in most cases. Members of the organization are also revealed that they get paid and can have their own evil piece servants.

Summary
Heartless was started centuries ago by former Leviathan in order to promise protection to the 72 pillars and to hold onto their loyalty out of fear of a civil war between the 72 Pillars and Great Satans erupting during the Second Great War. After the death of her and the original fifty members of Heartless, the organization continued to live on and has since then grown to one thousand members. While initially simply a group of devils chosen by Leviathan to protect the 72 Pillars, the group now has a actual ranking system and is more organized than when initially started.

Some of the Great Satans have revealed they would like to disband Heartless however due to pressures from the Bael Clan they are unable to do so out of fear of breaking the current peace between the two parties. Lord Rhaegar Agares is shown to be the Head General of the clan and it is revealed by Jasmine that the reason the clan can't seem to gain new members is because there aren't a lot of people that can deal with his strict and harsh nature.