This item is a tool, and potential weapon used by the priestesses in the monastic core of the Order of the Spider. Instructions on how it's used are kept very secret by the order as it plays a central role in its social structure, representing both the many years of training needed to wield it, and an intimate connection with the gods.
The fan consists of usually five ten inch rods, which are only held together by a strip of fabric running between them. Each rod is a small dispenser of fine dust powder, operated by a small mechanism at the base of the rod. Since the rods are not connected by a single screw at the base like normal fans the fan is very flexible, and bending it into a 'U' shape is often done.
The fan is also used as a sort of magic wand, being a focal point for Dust spells.
The fan is used by dispensing a small amount of dust and then using the fan to modulate the dust's location. Bending the fan into a 'U' shape, closing the fan, and employing multiple fans, all by an experienced user can lead to very precise manipulations of the dust. After the dust is placed in the air, hitting the ends of the rods together by opening or closing the fan causes a shock wave which activates dust around the fan and starts a chain reaction wherein a whole cloud of dust is activated.
In rituals the fan is used in things like divination. A common ritual is to cast bones onto a spell circle, release a cloud of dust, carefully fan it, and then ignite the dust. The resulting locations of bones and scortch marks are then interpreted as a message from the gods. Notice that when the priestess fans the dust, she could, with sufficient skill, greatly influence the outcome.
In combat the fan can hold dust of the users choice. Since the dust is so fine, an opponent may not even know that the fan user is setting a field of dust, and preparing to ignite it. Combatants may also want to have another source of dust since the rods can not necessarily hold much. Many choose some kind of wrist mounted dispenser.
A basic spell amongst the priests who use the fan is a sort of flair. This is done by bending the fan into a full cone, releasing appropriate dust into the cone and then using magic to ignite the dust into a flair bolt that moves to strike the opponent.
Fan users will sometimes use two fans; however, effectiveness can often be limited due to environmental conditions. This problem is limited in its traditional applications because the Order of the Spider would specially design rooms to make manipulation of the air easier.
The fan's significance in the Order of the Spider is caused by it's reliance on dust, and the fact that the Order of the Spider is very careful about who knows what dust is and it's capabilities.
Use of the fan is only taught to potential priests, with semblances and other features that could be deemed useful, such as a sensitivity for dust or air. The child must go through years of training as a priest, where in the fingers are trained to the required level of dexterity, before finally being introduced to the use of the fan. Only after much more training with the fan could the priest then engage in any kind of combat. An example of the fan's use as cultural tool is the belief that where a priest from the Order of the Spider walks becomes holy ground, at least for a short time, which is why people do not walk behind one. Many reports exist of a priest walking and when approached from the back by one meaning to aggravate, the priest will turn and request that the gods ignite the air behind her in fire, burning the aggressor.
This is, in fact, the priest's coy usage of the fan. While walking the priest fans herself and thereby constantly spreads dust behind her. In this way she is always prepared to display her divine power.
Another example is a priests dance with her fan's which are often accompanied by explosions and sparks. These effects are popularly believed to be the gods, taking part in the dance, but is, still a use of dust and the fan in particular. Performances like these convince most lay people of the priests divine favor. Fighters and other individuals who have come in contact with dust via the outside world may understand how these effects are actually done. However, even they know better then to try and expose the fan for what it is as this could risk the culture that incorporates it, and even lead to persecution and punishment by the lay people and priests themselves, respectively.
Most known users of the Hierophant's Beck would be members of the monastic core of the Order of the Spider, since they worked very hard to keep the weapon a secret. Its usefulness in open and chaotic combat is also questionable. Users of the weapon would usually have a semblance of particular usefullness to the task. It is unkown whether the semblance was a prerequisit to being taught how to use the weapon or if it is coincidence.