The role of Lucifer

In the cosmology of Lewis's Space Trilogy, as I understand it, each inhabited planet has a guardian angel. Mars is an explicit example. And Lucifer was the guardian angel for earth. 

Mind you, that schema raises the question of where the guardian angel was for Venus. Why did he not repel Weston, especially after Satan took possession of Weston? Seems inconsistent. What's the point of Venus having a guardian angel if he doesn't protect it from Satanic invasion and assault? 

But perhaps in Lewis's mind, the guardian angel couldn't interfere with the temptation. That had to run its course. 

Be that as it may, an additional point of interest is that Lewis's fictional cosmology may have an albeit very slender basis in Scripture. On one reading of Ezk 28, Lucifer is the guardian of the garden. 

That identification turns on a crucial ambiguity in the Hebrew syntax of v14. There are two ways to render it:

You were an anointed covering cherub

You were with an anointed covering cherub

Does it describe the fall of Adam or the fall of Lucifer? Is Adam the guardian of the garden? Is Adam depicted in exalted angelic terms–as if he's a cherub? Or is Lucifer the guardian? 

Does the narrative describe one character or two? Is Adam the guardian or is he with the guardian? 

Scholars are divided on how to render the syntax. And that in turn affects the identification of the figure(s) in the narrative

Suppose we go with the view that Lucifer is the guardian. That answers some questions or solves some problems. It explains why the Tempter was in the garden in the first place. It might explain why Eve wasn't surprised or taken aback by the Tempter–if he was a visible sentinel. It explains the reference to other cherubic sentinels in Gen 3:24–who replace him. And it explains why NT identifies the Tempter with Satan. 

What's the implied chronology? Presumably, Lucifer had to be created before Adam. And either created before God made the garden or around the same time God made the garden. So Lucifer was guarding it before Adam was created and put there. At that point he coexisted with them in the garden. He fell before or after Adam (and Eve?) were created. 

It's difficult to squeeze the fall of Lucifer (and other angels) into a six-day timetable. But if Gen 2 is separate from Gen 1, as a localized creation of the garden, that frees up more time (even assuming we regard Gen 1 as strictly chronological). 

That said, it's precarious to lay too much weight on an ambiguous passage of Scripture. But it does have the explanatory power to fill some gaps or tie up some loose ends.