The Emperor-Over-the-Sea is referenced at several points during the series. The Stone Table, Deep Magic and the Deeper Magic were all set in motion by him, and he is the father of Aslan.
At the same time, he does not directly enter the series; he does not appear to be present in Aslan's Country during The Silver Chair or the events of The Voyage of the Dawn Treader, and doesn't appear to directly intervene. He doesn't even seem to be present at the creation of Narnia during The Magician's Nephew or the Final Judgment in The Last Battle - the entire country was sang into existence by Aslan.
Given that C. S. Lewis was not a deist, why is this? Why was the Emperor-Over-the-Sea such a remote figure?