The Denarians are the good guys?

[groinkick]

Implication: Nic (at least) learns about Outside.

Nicodemus has been with Anduriel for around 2,000 years.  He knows about the Outside.

Harry hurt Uriel by calling him "Uri". The 'el' portion of their names means 'of God'. If verbally omitting 'of God' from his name hurts Uriel, imagine how being deprived of being with God hurts the Denarians. I can't imagine how any of them are still sane after thousands of years without him.

I don't think he hurt Uriel.  It was more like a major insult.  I'm not positive but I think it's because lucifer's name means Light bringer/morning star/ Shining one, and Uri meanings something like Light flame which is kind of similar while Uriel means God is my light

[groinkick]

You have to look at things from the Fallen's point of view.  Nicodemus probably does think he's saving reality.  In his own twisted way, he's right.  He's not realities friend though.

TWG, and his Angels are about ensuring free will.  The Fallen are against it.  They don't want mortals to have free will.  Nicodemus (in my opinion) is trying to achieve that goal, no free will.  In so doing he would save reality.  With no free will, mortals could not summon Outsiders.  They could not worship (and empower) Old Gods.  The forced worship of billions would create someone with such unimaginable power, no Outsiders could ever hope to breach the Outer Gates.

This I believe is his goal.  To become the new god of all humanity, and take away all free will.