They wanted the cure for vampirism. But in order to get it, they had to awake someone very dangerous that could kill us all. However, if they killed me, they killed my entire sire line. Long story short: Jeremy Gilbert was a vampire hunter, The more vampires he killed? A tattooed map appeared on his body revealing the location of the cure. Killing me killed thousands of vampires in one fell swoop, and bam, location to cure city.