Finish This Puzzle!

I remember a word puzzle of sorts with origins in the Middle ages:

R O T A S
O _ E _ A
T E N E T
A _ E _ O
S A T O R

What are the missing words, and what is this puzzle supposed to mean?
(I think its supposed to be some kind of password for the Crusaders in the Holy Lands, but I’m not sure)

A search on google for rotas sator produced a bunch of links, including http://smithtrust.com/satorsite/pages/SATOR.html, which gives:

S A T O R = god or savior
A R E P O = plough
T E N E T = rules
O P E R A = the works of man
R O T A S = creation

I noticed a link from the parent page saying that the earliest known example was found in Pompeii. Dunno.

I remember seeing this a long time ago.

I think it goes the other way

S A T O R
A R E P O
T E N E T
O P E R A
R O T A S

It’s some sort of magic square. It reads the same across as down. It supposedly has some power over witches and I think it can put out fires if you engrave it on a plate and throw it into the fire.

It means something about he who turns the wheel. . . I forget the rest.

I’m going from memory, so don’t blame be if it doesn’t stop a witch or put out your fire.