Crimson Covenant

While the typical abactor does not receive directions from anyone, some, such as High Priest Malevanor of Atur, answer to a secret council of undead known as the Crimson Covenant. The group’s existence has become a matter of public rumor since Moranna’s repudiation of the religion, but the details of its membership are the subject of conspiracy theories; some suggest that the Crimson Covenant are direct agents of Lady Illmarrow, others suggest they’re interlopers from Mabar or Dollurh. Some even say that when a powerful member of the faithful uses a divination spell like commune, the divine proxy that answers is one of the Crimson Covenant.

In truth, the Crimson Covenant is a group of thirteen former mortals founded well before Lady Illmarrow took an interest in the Blood of Vol, with several members older than the Kingdom of Galifar and its head, the demilich Duran, older than Karrnath. Over the centuries, Illmarrow’s agents infiltrated the group, ensuring it would be pliable when the time came for her to dominate Karrnath. Moranna’s revelations about the lich’s influence have shaken the members of the Covenant, who no longer trust each other as they question their relationship both to the faith and to the political divisions within Karrnath. Some within the Covenant argue that Lady Illmarrow is an important patron the group should try to work with; others argue that she has given herself fully to the power of Mabar and must be opposed.

The majority of the Crimson Covenant members reside within Atur as oathbound mummies alongside their leader Duran. Some of the other members, such as the Silent Knight, are free to leave the city. 

Source: Cultures of Karrnath

Among most of the faithful the Crimson Covenant is little more than a legend; most seekers believe that Hass Malevanor, High Priest of Atur, is the greatest spiritual leader of the faith. There is good reason for this secrecy. First and foremost, there are many—the Aereni Deathguard, templars of the Silver Flame, paladins of Dol Arrah, and other champions of the light—who would see these elders as monsters to be destroyed. But there is another aspect: all undead aren’t created equal. We think of things in terms of stat blocks and rules, under which a lich is a lich is a lich. But the necromancy of the early Seekers was adapted from Aereni techniques; it was never as sophisticated as the techniques used by the Bloodsails or the Line of Vol, and has its own quirks. The most ancient member of the Crimson Covenant, Duran, was its first lich; but while his will is strong, his enchantments are unable to maintain his body and he exists now as a demilich. Most of the members of the Crimson Covenant are oathbound, and many of their oaths are quite restrictive. Beyond this, many members have had their humanity slowly worn away by the passage of time, and they know it; it is difficult for them to interact directly with the living. With this in mind, Malevanor ISN’T a member of the Crimson Covenant; he is still young, still comfortable with the world. But he and other priests protect the Covenant and rely upon it for guidance, and the Covenant does perform the most sacred rituals of the faith. The core of the Covenant resides in the catacombs below Atur, and it is their devotions that contain and channel the dreadful powers of this sunless land.

So for the most part the Crimson Covenant are masterminds and advisors. They can cast spells and perform rituals that are far beyond Malevanor’s powers—but only a few of them are actually capable of freely moving within the world. As such, they generally support the faith by creating magic items, raising undead (they were certainly an important part of raising the first armies for Karrnath), and casting divinations and other rituals. They teach the most promising students in the Crimson Monastery. But there are only a few—such as the Silent Knight and Lady Dusk—who often act in the outer world. There have been others—there were a few members of the Crimson Covenant who rose from their chamber to lead Seekers in the Last War—but they have been destroyed.

Source: http://keith-baker.com/crimson-covenant/ 

The Crimson Covenant is Erandis Vol's thirteen most trusted lieutenants and advisors, responsible for executing her global plans and machinations. Handpicked over the centuries, each member is either an undead or has some other method of unnaturally extending their lifespan. While each member has taken their own extensive set of steps to protect their person both from physical and magical harm, Erandis has supplemented their defenses with her own rituals and spells, protecting not only their identities but very existence from mortal magic.

While the Lords of Dust or Dragons of Argonessen might be capable of piercing Vol's defenses, either they have simply not thought to look or have their own reasons to let them be. It is possible that one or both groups may have a deep cover agent amongst the thirteen, subtly manipulating Vol and her plans to fulfill key passages of the prophecy.

Source: Politics of Eberron