~ He goes by many names: The Forgotten Merchant. The Merchant of Oblivion. Or simply, The Merchant. The reason for this name is quite simple. He traps people into making an unbreakable vow, which at its core is also very simple: the acknowledgement that they owe him a debt (via contract and witnesses), and vow to repay that unspecified debt when The Merchant so chooses.

But of course The Merchant needs more than an Unbreakable Vow. After they make the vow, the memory of their Vow is withdrawn from their mind and put into a Pensieve as collateral. Then, a memory modification charm is placed upon them so they don't remember taking it, and don't remember the witnesses. The rules of the Vow still remain however; the fact that the vow is for an undetermined act prevents them from perishing. Only when the memory charm is lifted are they in danger if they decide they want to go back on their Vow.

Even those who do communicate directly to the Merchant don't know his true identity because of Polyjuice Potion. In the rare instance the potion wears off, another memory charm is placed upon them. Those who are aware of this flaw do well to avoid having a memory charm placed upon them: too many charms means a greater likelihood of permanent damage.

~
THE MERCHANT:
deals in information, blackmail, cursed objects, stolen objects, weapons.
highest ranking members are Bishops, who will remain NPCs for the time being
tends to leave anyone underage alone in terms of recruitment and targets, but that doesn't mean they could be affected by the fallout.
The Merchant will send messages to Couriers and Pawns via owl written in ink that only they can see. To keep a paper trail, they must sign the letter. After it's signed, the letter disappears and returns back to the merchant for record keeping.

ROOKS: skilled in magic, especially the dark arts and memory modification. Their memories are kept, but they are bound by a magical contract.

COURIERS: They have no authority in the hierarchy however are permitted to keep their memories and are bound by a magical contract. They willingly carry stolen goods back and forth in addition to keeping an eye out for potential vulnerables to bring back to The Merchant. They are paid by the goods they bring in.

PAWNS: those who have gotten locked into the contract; the memory modification spell has been lifted, and they are awaiting instruction

OBLIVIATED: those who have taken their vow, and have had their memories modified; they do not remember a thing. they could be called upon at any moment.

TARGETS: they are ideally vulnerable, have nothing to lose

You can see a hierarchy of The Merchant's organization here.

ROOKS Jay Fox Agrimony Macnair Adrestia Dantes Name	COURIERS Hestia Name
PAWNS Luna Wakefield Name	OBLIVIATED Gwendolyn Vane-Tempest Name
TARGETS Arthur Pettigrew Isis Silverthorne Name	STOREFRONTS The Ivy Leaf — Diagon Alley Curios Apothecary — London Name