If "souls" existed, unless you mean one of the traditional "being" meaning, it makes no sense to use machines to "probe" it, because in its usual metaphysical doctrine, it would not be physical. The second paragraph, about "stealing souls", appears to be about that imaginary soul, a human "spiritual" invention to describe consciousness for those ignorant about its function and origins. So basically, and that's classic in UFOlogy, your "Gray" is just a revamped demon of Christian superstitious tradition. Then it's always been very ironic why supposedly distant civilizations would have to be about humans and their old traditions. The only explanation is of course, that this is too, human tradition and mythology. Then one should remember that those concerned about "stolen souls" are really only throwing frivolous heresy accusations, because they want to manipulate with specific doctrines. When those are rightfully rejected for having no basis or legitimacy, it must become dramatic, to advocate for the oppression of the dissenters. Bullshit exposed.
I wondered, maybe #mammon would fit?