The seventh ray is the counterpart of the sixth and the one Bailey's system says is coming in. Its quality is ceremonial order: ritual, organisation, and the specific work of joining spirit to matter so that an intention takes physical shape. The scheme calls it the ray of magic in a deliberately unromantic sense, meaning the discipline of arrangement, of getting the form exactly right so that the form can carry something.
Bailey ties it to the Aquarian age the sixth ray is said to be vacating, and the pairing is doing more than astrology. The claim is that devotion is being replaced by organisation as the characteristic spiritual mode: that the coming form of religious life is less the solitary aspirant and more the group working to a shared pattern. Whatever one makes of the forecast, it accurately describes a great deal of what the twentieth century esoteric revival actually built, including the ceremonial magic of the Golden Dawn and its successors, which the atlas records elsewhere.
The named shadow is formalism, the ritual performed perfectly with nothing behind it, and bigotry about the correct way to do things. The seventh ray is also the one most vulnerable to a criticism the scheme invites: a ray defined by order will always be able to point at order and claim it.
Like the other six, it is modern. The sevenfold pattern reuses older sevens, the planets and the days among them, but the ray scheme itself dates from Blavatsky in 1888 and Bailey from 1936.