(This setting writeup is inspired by Jeff Somers' 2013 urban fantasy novel Trickster and is presented here as a homage to an excellent book. I recommend that you read it.)
Spells and Spell Hacking:
Magic is divided into Cantrips, mu, and Rituals, biludha. Cantrips can be powered by small amounts of blood, while Rituals require much more.
Spells have a verbal component along with the material (blood) requirement. As a result, gagging a blood mage always prevents spell-casting.
Certain mages have the ability to hack spells, remove syllables to cast the spell faster or replace syllables to modify the effect of the spell. In one example, a hacked light spell was modified to create 16 variations and three syllables shorter for a quicker casting. This is considered a War Talent, as a shorter spell is faster to cast and more valuable in a combat situation.
Blood and the Drawing of Blood:
Blood is used to power all spells. The more blood, the bigger the effect.
Usually the mage cuts himself or hires someone to cut themselves for the blood. Penknives, switchblades, daggers, shivs, needles or any other stabby/slashy implement that will allow them to quickly draw their own blood are employed. Most keep a dedicated weapon for this purpose.
Mages can also use any blood spilled around them and can even steal the blood from other mages or mages' bleeders during a magical duel.
Blood is referred to colloquially as gas. which could be related in the magical language to gasam (master).
A student mage takes an oath to become the urtuku, the apprentice, of an established mage. Their gasam, their master, teaches them the ways of blood magic.
Apprentices are magically bound to their master and only death (of either) or the master himself can release them from the oath.
Mages know intuitively if someone is bound by the urtuku oath and will not and cannot take that person as an apprentice until he is freed.
Most apprentices stay long enough to learn all they can from their masters. Some stay even longer, hoping to get all the knowledge they can. If an apprentice leaves without his master's assent, he is still under the oath.
There are several ranks of blood mages. The idimustari, the Tricksters, are at the bottom. They use small amounts of blood to cast Cantrips to con the mundanes. Some are highly skilled but most have limited abilities due to lack of training or raw talent. Lem and Mags are examples of idimustari.
The ustari are the full-rank Magicians. They can cast mu as well as more advanced spell rituals, biludha. Hiram Bosch is an ustari.
Bleeders are lesser mages, usually idimustari or ustari, that bleed at the command of more powerful mages. While even idimustari and ustari can hire non-mages to bleed for them, these hires are not considered Bleeders due to the lack of magical skill. Bleeders are well compensated for their service but risk the ever increasing chance that their masters may empty them of blood.
Saganustari are powerful mages, often having Bleeders to provide the blood for their spells. Cal Amir is a saganustari.
Enustari are the Archmages, the most powerful mages in the world. They have legions of bleeders and often cast spells that result in mass death events around teh world. The most powerful enustari is Mika Renar. Others encountered in the book are Faber Gottschalk (Hiram's gasam) and Evelyn Fallon, a Fabricator.
Fabricators, Magical Items and Constructs:
Fabricators are blood mages who create magical items. These include devices that power big biludha and often take years or decades to construct. Fabricators rarely take apprentices as they are jealous of their magical secrets.
Powerful mages can create dimma, a construct that fits the legendary standard of a golem. It is unknown if a Fabricator is necessary to do this as information on their construction is scant.
Mages and Technology:
Blood mages eschew technology, avoiding computers and most electronic devices. They don't seem to have any hex or jinx capability towards higher tech but they are uncomfortable using it more than rarely. Cars, guns and common household appliances seem to be the exceptions.