The Michaela factor is a mysterious, likely naturally present factor in some humans’ genetic makeup that only very few boys carry that makes them special, “chosen” in some way. (a similar ask was here) Allegedly, it also imposes some sort of damned fate on the carriers, and as a side-effect, apparently makes the blood of such males extremely delicious to vampires. Known carriers: Ferid Bathory, Crowley Eusford, Hyakuya Mikaela. Also, possibly, all the carriers are highly gifted men, from looks to intelligence.