The Black Crusaders, since it's creation, have utilized kidnapped children to use as test subjects in the research for their Pursuit of Power. While thousands of children and adolescents are stolen from their families, only very few survive their dangerous and often torturous experiments.

Initially, X was so invested in finding a way to synthesize nymphid abilities, at first so he could find a way to use sylphic abilities, but he eventually learned it would be more valuable to find a way to give humans abilities, as well as manipulate their minds to make them better soldiers and grunts. His first successful synthesized human would be Vi, because her twin brother, Io, would provide perfect transplant organs for the organs damaged by the transfusion. Cat, Birde, and Zeph were the first successful animal transfusions, using preserved but dead humans, however, they needed to be taught how to speak, walk, etc, so they had to figure out a way to transform living humans into nymphs.

The first successful living animal transfusions would be Jace (and Azazel), Connor, Leo, and Felix. After these four, the animal nymph symbiosis process was much more understood, and became much less risky. The process, after being developed and tested on hundreds of children, became much more understood and the process now had no fatalities after being perfected. It would soon become a sought after privilege to be given powers in the Black Crusaders.

While Leonidas/Lee was in charge, the Crusaders kidnapped many, MANY more children, and even adults, to be used as test subjects for various Anthracyllin implements, as Vi was an addict and wanted to find more ways to harness the drug. The tests had such a high mortality rate that anyone who was kidnapped by the Black Crusaders at this time were already pronounced dead. This era of research leads to much better understanding of Anthracyllin's effects on humans and nymphs, and leads to more variations. The newer version of the drug, in its more dangerous and imperfect form, is the most addictive strain, and would cause many of its users to overdose, the only formula of Anthracyllin to do so.

Under Antoinette's reign, the Black Crusaders kidnapped far less people, as there wasn't as much demand for them. Instead, they gathered already vulnerable individuals that would seek the power of nymphs and opportunities to test their powers or inflict pain and suffering on others. The only demand for human bodies, after the interest on Anthracyllin began to fade, were for the Clones experiments, which required blood, tissue, etc, on a case-by-case basis. This leads to Conre's creation, and his exceptional intelligence causes a slight resurgence in kidnapping rates, however, their targets were no longer random humans. He wanted to modify people of different raises in pursuit of the creation of a Janus, but he would never be successful.

When Kieran took over, he let Conre use all of the resources at their disposal to try and create more and more powerful variations of sylphs, nymphs, humans, and crosses of some or all of them. Kidnappings became more specific and much less common.

As soon as Dami took charge, kidnapping basically stopped, because his Pursuit of Power was directed towards himself, rather than the growth or the organization. This caused the Crusaders to shrink significantly because of no growth as well as desertion, specifically because the people there for the cause didn't believe Dami was aligned with their original cause.