The Ancient of Days, the Father who is in secret, is found in the First Space.
Nature, which is explainable only with the Sixth Mystery, is found within the Second
Space. Excerpt from the book: The Pistis Sophia.

The first triangle of the tree of life (father son and holy spirit) descending from what is called the sacred absolute space is entirely spiritual. It exists in what is called the first space or Atziluth. The domain of archetypes.

The second space is The World of Creation - בריאה Briah.

The sixth mystery is related to sex, and the creation of the human soul. The human soul is the result of divine sexuality also called chastity.

Lucifer is the entity of the semen, the first created angel of the united Elohim, or god and goddess in Binah.

The question is where does Lucifer reside in the tree of life?
Is it in Daat the hidden sephiroth?
What role does he perform in Binah?