So, first and foremost: blood magic is not evil. Get that idea out of your head, it’s a pretty popular practice in European folk magic and within African folk magic. It’s powerful but that doesn’t make it evil. Unless you equate power to evil in which case maybe you shouldn’t be here?
Blood has a lot of power and associations behind it so think of it like throwing a molotov into your spell when you want something done. you could also just charge the sigil with your blood.
Blood is just the most basic pure form of our energy. You can dab a small amount of blood at the center of sigil while charging it and here you go.
Your blood is basically a manifestation of your life force and energy in a spell. Blood can represent your family ties and therefore can be used as part of multi-generational cursework to really teach a bitch a lesson if needed. Blood magic also ties you to your spellwork forever so, if you want out, make sure you can destroy the blood used in the spell or follow the related methods within your own culture/practice to eliminate those ties to you.
In short, if you use your blood in something, your fingerprint is on it and an adept energy worker or cunning person could trace it back to you. You can mask your work, of course, but people can go through the proper channels and figure it out eventually if they’re heavily invested in that shit. So, short hand – I personally discourage the use of blood in cursework.
So, blood magic holds the charge – the intent, the energy, whatever you imbue it with – forever. Or for as long as you let it. This keeps it from fading over time and that can be both a good and a bad thing. You see if you want your spell to last a lifetime or more, use blood. I’ve got family members that have worked blood magic into their spellwork and it still carries a charge even after their death. It’s amazing and empowering when used in the right applications.
What can I use it for?
Blood can be used for literally anything you want – offerings, divination, sigils, cursework, initiation ceremonies… whatever you want, really.
You want to spice up your grounding ceremony and tie yourself to the sense of calm you experience? Toss in a drop of blood during your ritual.
Wanna tie yourself to a patron deity or make a serious oath? Toss a bit of blood into that ceremonial chalice as part of your ceremony.
Wanna add some strength to your sigils? Add a drop of blood to your ink or whatever your medium and fucking go for it.
So, where you get the blood also matters. Don’t be retarded and take a machete to your wrist. A diabetic lancet work excellent!
Menstrual blood can be used for hella strong fertility magic. I’ve seen people also screw people over with this in terms of their sex lives and having kids so like the applications are pretty solid. You can also ward against pregnancy with this shit.
Blood drawn during a fight can have a fuck ton of passion and anger behind it, which is amazing for spells related to courage, strength, and power. Also great for confidence and glamour-related spells to make you seem larger than life.
Blood drawing during sex is hella hype for sex-related magic and offerings.
Lots of options, lots of applications. The correspondences will vary depending on what folk practice/religion/whatever you subscribe to but some shit overlaps. In order to acquire blood, lancets, sanitized knives and needles work quite well. Please be safe as we do not want to risk infection.
A little blood goes a long way. Seriously, you don’t need like a fucking goblet of blood as an offering. A drop will suffice. Blood is the ultimate element, the life essence of the practitioner, and it can be used in place of any ingredient.
My only concern is that when cursing your biological family, using your own blood ties you to the curse. Since his blood runs through your veins, there is a high chance of it influencing you as well. You can put failsafes in place to prevent this, of course, but it’s a possibility that you would want to take into consideration.
My personal recommendation would be to use the blood to empower a related task – perhaps as an offering to a deity or demon you work with – to aid you in this quest. And then you could do something else afterward.