[Suzerain of Sheol]

The device had nothing to do with it at all. It's for calling down a nuclear strike from the Amorpha satellite, it's extremely dangerous to have it just lying around.

The illusion was dispelled when Sin recognized Na'lsa's presence -- he is one of her many children, being the incarnation of one of the Seven Sins.

And I imagine she strikes you that way cause you've never read Paradise Lost. :|

On either side a formidable shape;
The one seem'd Woman to the waste, and fair, [ 650 ]
But ended foul in many a scaly fould
Voluminous and vast, a Serpent arm'd
With mortal sting: about her middle round
A cry of Hell Hounds never ceasing bark'd
With wide Cerberian mouths full loud, and rung [ 655 ]
A hideous Peal: yet, when they list, would creep,
If aught disturb'd thir noyse, into her woomb,
And kennel there, yet there still bark'd and howl'd
Within unseen. Farr less abhorrd than these
Vex'd Scylla bathing in the Sea that parts [ 660 ]
Calabria from the hoarse Trinacrian shore

Which is turn lifted from Spenser's the Fairie Queen in the character of Error.

And are you not thinking of Lamia? Lilith was apocryphally the first wife of Adam and was eventually damned and became a succubus who murdered newborns.

And she has feathered scales because she's a clone of Satan. :|