Ghost
The Ghosts are the most accomplished members of the Reapers. They have been members of the organization for many years, and have made decisions that helped the organization prosper in some way.
Ghost is not a title that is given to just anyone who has served the Reapers for a long time. It has to be earned, often through some form of self-sacrifice, though no one has ever been granted the title of Ghost posthumously.
Qualifications
The only specific qualification the Reapers have for someone to become a Ghost is that they are a Reaper (and a great one, at that).
Beyond that, a current Ghost must recommend the Reaper in question for consideration. The Ghosts then confer, determine as a group whether the individual in question would be a good candidate for the title. If they are, then a short ceremony is performed, given them the title for the remainder of their time in the Reapers.
Requirements
There is no minumum time of service one must achieve to receive this title, though most (if not all) Ghosts received the title after 5 or more years of service. Some Reapers are granted the title after killing a close relative or friend quickly and efficiently (in addition to a considerable number of successful assignments beforehand). Others receive it because of the incredible job they have done training groups of future Reapers. The majority of Ghosts, though, have received their title simply from many years of dutiful, effective service in the organization.
Appointment
There is a short ceremony performed when the title of Ghost is conferred. It consists of their old, black Reaper cloak burned in a small pyre, after which they are granted a new, silver cloak, with a clasp that demonstrates their new station.
Because of the inherent secrecy of the organization, as well as the humility that Reapers tend to possess, these ceremonies are quick, and typically there is not much celebration of the new title.
Duties
The duties of Ghosts remain largely the same as whatever they had prior to the title. For instance, a Ghost who previously had the job of training new recruits maintained that position, if they wished to. However, Ghosts are the leadership of the Reapers. As such, Ghosts are given the opportunity to assist each other in making decisions for the organization, including who should be recruited and what jobs they should undertake.
Ghosts are, additionally, in charge of promoting other members of the Reapers to the same status, as well as keeping an eye out for any members who do not belong in the organization. Therefore, Ghosts much also keep a close eye on all other Reapers (including other Ghosts) for any behavior that should be praised or must be repremanded.
Benefits
Ghosts are capable of affecting the most change anywhere in Arratha. This in and of itself is a benefit of the position, as Ghosts hold sway over everything. In addition to these innate benefits, Ghosts are provided with more luxurious quarters, as well as more money and, often, high ranking political positions. These positions afford them the reasons necessary to be out and about in public, assessing what matters require the Reapers' attention in the future.
Accoutrements & Equipment
Ghosts are provided with silver cloaks, complete with a platinum clasp in the shape of a staff and a rapier crossed over one another. However, these items are hardly worn by Ghosts, as their title is unknown to all but other Reapers. As such, these are worn during events specific to the Reapers, but outside of that, they are encouraged to wear whatever would make sense in whatever situation they find themselves in.
Grounds for Removal/Dismissal
Ghosts are hardly ever mistakenly appointed, as they have shown great commitment to the Reapers for years. They are, however, still under the close, careful watch of the other Ghosts. If they make a decision that is viewed by another Ghost as truly out of line with the tennants of the Reapers, then all Ghosts are called together to discuss the action, and determine if the person in question should be punished based on the actions called into question. If they are, then they are removed immediately, with prejudice.
They are killed, and their body is disposed of in a way to never be found, so that no one ever knows what happened.
This has never happened in the history of the Reapers, but it is a policy that all Ghosts know, and all of them fear.
I really like the consequence if the Ghost does something against the tenants of the Reapers and how other Ghosts watch and observe them, I imagine it might be both a privilege and a bit nervy being a Ghost (even if Ghost's have never actually been punished - although it doesn't sound like it would be difficult for the Reapers to cover up a Ghost being punished).
That's exactly what I was going for. It's actually unclear if these consequences have actually been carried out or not, even within the internal recorded history of the Ghosts. Some Ghosts especially think that the rules and procedures are a bit too well thought out to be a "just in case this comes up" sort of idea, but, when there's no proof, you can only assume it's never been used. Definitely a worrying position to be in, as well. It helps a bit with the whole "absolute power corrupts absolutely" idea as well, since that power is only maintained by using it properly, so it's not quite absolute (though it is darn close).