It common for mages to tattoo spells or marks on their body to serve as automatic casting in times of emergencies. I have tattooed personalized symbols on my body that I can call circles by making a symbol or a word without having to do all the work to open it down. I have also tattooed symbols for beings to be available on command to use as servitors and happy helpers. The marks have purposes and preprogrammed tasks that are determined by those who draw them. Tattoos in my opinion are the highest form of blood magick that a person can do as it seals a contract between entity and castor. A warning though, once a contract is made it is eternal and cannot be broken so be careful of what vowels and pacts you make before getting the symbol tattooed. Also don't be like most hip people and get a symbol that you think looks cool, without knowing what it is. Cover ups don't break contracts.