The Definitive Answer to Palpatine's Face in ROTS

I'd like to know how you Force mask your face and "bad aura" from Jedi with you in the room.

 

Well, TOS has confirmation that it's a mask.

 

That was almost as funny as last week's Tam's Excellence impersonation!

 

Here's my (slightly revised) take on it:

I believe that the Dark Side had aged and possibly even deformed Sidious repeatedly through the years, and each time he had managed to fight it back with his Dark Side skills, reclaiming the face of Palpatine. This explains why he looks older in AotC then he does in RotS. In AotC "the shroud of the Dark Side has fallen" but the cost can be seen on the Chancellor?s liver spotted and sickly looking visage.

Sometime after AotC but before RotS, when deaths from the Clone Wars and defections from the Jedi order have strengthened the Dark Side, Sidious is again able to fight back these effects, once again reclaiming the features of his chronological age.

When Mace reflects all of that Dark Side energy back at Palpatine in RotS, Palpatine absorbs it to avoid taking damage, the same way that Yoda absorbs Dooku's lightning in Episode II. However, the sheer amount of Dark Side energy involved not only instantly ages and deforms Palpatine, but also permanently scars him to the extent that he will never again be able to use Dark Side magicks to reclaim his features.