Chamild Organs are a biological organ that certain Beasts posses. They can bend light and change atmospheric opacity, which essentially allows the equipped Beasts to become invisible. This also conceals the entire planet surface, thus, when used alongside Jamil Organs, they can prevent most forms of orbital observation, isolating an entire planet from space.
Since the production process is more complicated, these are not encountered very often. They're mainly installed in Guardians, though they've also been seen in other special Beast units.