Vampire sh*t, the energy and essence of children are pure, and one of the best "magickal" ways to transfer energy is via sex and via blood. That's why Satanists are all about orgies, sexual energy in of itself is the most powerful form of energy a sentient being has in this incarnation. Basically the more kids they commit pedophilia with the more energies they absorb, so the more "magick" they can do, similar to how the more blood a vampire gets the more energized he is. I imagine the people who are at the top of the food chain probably commit copious amounts of pedophilia on a yearly basis.