Planets As Shields

I can't find it now but somewhere in A Stone In Heaven, one of the moons of Ramnu was like a shield, resembling a shield in shape and also concealing and protecting Hooligan. I meant to quote this when posting about planets seen from space. 

CS Lewis imagined that Earth's Moon was:

"'...as the shield of the Dark Lord of Thulcandra - scarred with many a blow.'"

-CS Lewis, Perelandra IN Lewis, The Cosmic Trilogy (London, 1990), pp. 145-348 AT 17, p. 338.

Thus, Lewis incorporates lunar craters into his fictional mythology. He also finds a place for the "canals" of Mars and the supposed oceans of Venus. In haste. Back here later.

Addendum

Correction: It was not a Ramnuan moon but Ramnu itself that became a shield:

"Hooligan curved around and departed from Ramnu. The planet became a shield, emblazoned azure, argent and sable, against the stars."

-A Stone In Heaven, XII, p. 166.

The emphasis is on the appearance of Ramnu as an emblazoned shield, not on the planet as shielding Hooligan.