What is a Weaver of Fate? 
Sapphira is the only known Weaver of Fate of her species - she has gone under other names, but each time they have been her. The Weaver's job is to guide the fate of those around her, to help join them with groups that are friendly to their purpose. To lead them to their "rightful path", or to take the correct course of action. A guiding star. 
Of course, she cannot help everybody. There are far more strands of fate than she could ever handle alone. She cannot prevent wars or killings, only guide those that may cause them away - if she comes into contact with them. At the end of the day, it is the owner of that strand that has full control of their destiny and it is their choice how they live it; she can only offer advice. 
A thread of fate becomes tangled when outside sources badly effect the owner of that fate, to the point of becoming a destructive mess. This knot can catch other threads that were previously safe, destroying their lives in that person's downfall. Sapphira see's it as her duty to untangle those knots before they ruin more lives. That said, a person who kills many may have a completely clear thread of fate, it was simply what they chose to do without outside influence. Someone with a completely tangled thread may not become a killer to anyone but themselves. In a sense, she could be seen as a guardian angel - there to give advice and connect when life seems too dark to continue. 
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Then what is her purpose? If she cannot prevent people from doing bad things, what's the point? 
People are not inheriently born evil; even their destiny is not set at birth, not truly. Their upbringing, lifestyle, culture - they are all guiding factors that can cause a thread of fate to become a tangled mess of destruction. Sometimes, meeting someone who is completely harmless and 'good' can cause a knot - it all depends on circumstance. Sometimes, it can reach such a stage that the knot can never be untangled - and so it must be cut. 
Sapphira cannot do the cutting. She can only work to help remove the harmful factors of a person's life, attaching them to others who would instead weave their strand with them rather than knot them all up. Sometimes, there is nothing she can do but try to make the end comfortable. There are other Sirens who kill in her name, when the needs must. 
Even if she can only save one life during her lifetime, she considers it a job well done. Every strand is important to her; from the thick to the thin. She's not there to only get involved with the 'important' people - protagonist or not, she will extend a hand to help. 
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Saving lives is a noble cause, but surely sticking with the 'protagonists' would save more lives in the end? Wouldn't that be a better use of her time? 
Every life is important. In the great weaves of history, every colour makes the picture - it doesn't matter if one thread is thicker, or in a more promenent place, it could not exist without the smaller threads holding it up. Sapphira sees life in a similar way. Consider the butterfly effect - killing one thing in the past that was not originally dead causes a ripple in history, sometimes completely changing it's course. There is no way to know the future, and she certainly doesn't know it herself - so why waste time worrying about the lives that could have been saved instead of saving the lives she could at the time. 
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So basically, she's a glorified counsellor? 
To a point, yes. A counsellor has a harder time of it - a lot of her healing is done not only by talking and advice, but by meditation and magic. But in the simplest of forms, thats what she is. A counsellor who can 'see' some connections without being told they exist. 
It is this vision that makes her so useful to royal courts, or lawmakers. Noticing the connection between people without a word being said can prevent spies, spot an alibi to a crime, notice love affairs and such. She cannot see the future, or where those threads might lead - only that they exist and weave the way they do at this moment. Her magic can be used to force the thread to 'confess' - speaking the truth as they see it from their very heart. This is seen as very dangerous and is rarely done, as she must bind her soul to theirs in a temporary manner. The imprint left behind can be fatal, leaving the original owner of the thread as a husk who only sees their duty as serving her. Sapphira views this act as something against her calling, so will only do it when it will help several other threads or under the force of her host. 
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Can thread 'connections' be hidden to her? 
It fully depends on the amount of time and concentration she's able to give towards the person. She does not get all the information on their life from a single glance - reading threads takes time. A willing participant can give the basic information to her via a long touch, with full information on their threads granted within an hour of meditation together. One who is hiding their thread takes longer; a fifteen minute touch may give her the very basic information if they are not practiced in shielding themselves, longer if they are. Such shielding can be broken however via various spells and potions, and of course - time. Time is the largest factor. 
Courts that use her or one of her 'Children' tend to have the participants of the trial swear to open their hearts to the Siren instead of swearing on a Bible or other religious item. During this process, they must touch the Siren's hand [or, if the Siren has one, their natural gem - for example, the star gem on Sapphira's chest] and repeat the oath given to them by the court. The Siren then stands to the side and watches over all proceedings. If any of the participants are shielded, the Siren states this before judgement is made. The judge or jury can ask for the Siren to spend more time breaking through the shielding, though such things are generally rare. Though the word of a Siren is taken highly into consideration, it is not law, and may other factors come in to play. 
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'Children'? She's a mother? 
No, no. There are Sirens who are born with the calling to follow in the footsteps of the Weaver; they are known as Weaver's Children. In most cases, these Children are taught by Sapphira herself on how to see and interact with the threads of fate, teaching them her art to the full extent of their power. If Sapphira cannot return home in order to teach them, they are taught by the Children as a group. 
The teaching process takes quite a lot of time, and involved the Weaver binding her own thread to theirs - while this is usually a dangerous and destructive act, Weaver's Children are instead 'awoken' by this process. Being awoken allows the Child to see the threads of fate themselves, which can be quite shocking for the first few days. From that point on, they learn how to control their sight as well as work with the threads themselves. Overall, it takes a lot of meditation and practice. 
Once trained, the Weaver's Children are free to do as they wish; some choose to stay on the Siren home planet to take part in ceremonies and other duties; others choose to find a host to work for, generally working in royal courts or lawmakers; some devote themselves completely to the medical field and saving lives. They are highly wanted, and never have trouble finding a place in society. No matter their choice, however, they will always return when the Weaver calls to act as her handmaidens. Such a call is pretty much unheard of, and hasn't happened within any currently living Siren's lifetime. 
All Children adhere to the same basic calling as Sapphira; to guide. To untangle as many threads as they can. They are also bound by the same inability to cut the threads without help; a different sect deal with that. 
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A different sect? 
Guardians of the Weavers; its more of a job title than a sect, though becoming one is seen as difficult. Anyone from any Cove can become a Guardian, though most come from the Cove of the Blood and the Cove of the Heart due to their values. The family who started the Guardians many lifetimes ago, known by the title Darian, still follow the tradition of becoming Guardians with each generation. 
A Guardian acts as the axe for a Weaver when they need to end a life. This is not done in a violent manner; those that cannot be saved are heavily mourned for, and rituals are cast to give them the best end of life possible - even if they fight back against death. It is this act that takes up most of a Guardian's training while being seen as the hardest part to do. Other than that, Guardians take up the natural job of protecting a Weaver from those who doubt their powers, or wish to abuse them. Some become hand maidens, taking on domestic care roles for the Siren while still keeping an eye out. All Weaver's Children have at least one Guardian. 
It is not unusual for a Weaver to become bonded to their Guardian [or Guardians] due to the close nature of their relationship. This is welcomed and celebrated as much as any bonding that happens. 
The Weaver herself is allowed to take on as many Guardians as she wishes, and has done so in the past - though currently she owns no personal ones. Instead, while visiting home, the sect designate a special party of Guardians to care for her. 
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Right, right. So, can only Sirens become Weavers and Guardians? 
Yes and no. Only Sirens can become Weavers in this sense of the word; others may have similar powers and may be able to do all of the things a Siren Weaver can do, but Sirens themselves would not consider that person a Weaver of Fate. In their eyes, only their species can take on the mantle. Therefore, the name would not be given to one of another race. 
On the other side of things, anyone from anywhere can take on the mantle of a Guardian; in fact it's heavily encouraged. Guardians of the Weavers are incredibly friendly towards anyone who wish to protect their charges, and will happily teach another how to do it properly. 
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Alright! That's all for now - can I come back if I have any more questions? 
Of course! Feel free to message any extra questions you have. I'll be happy to answer them! 
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