Flesh Magic, also known as Blood Magic, was a kind of magic based on the employment of flesh and blood to perform spells and rituals. It predated word-based magic and was considered by some to be more powerful. A demonic zealot attempted to summon his worshiped entity by using flesh magic which involved cutting a person open and taking their innards. The being, not to the demon's knowledge, was a vampire, therefore couldn't die in the process and the spell itself didn't work.