If you are looking for more Winternight lore and info:
Threats (2e) has large write up for Winternight.
System Failure (3e) the full Winternight plan, how it was to go down, why it was to go down, and what went right and wrong with their plan...
Threats 2 (3e) as I recall had some more info of Winternight. Sadly its one of the few I don't have on PDF So I can't double check.
But they all stress one thing. That Winternight was unique in both its structure, AND its membership.
Also remember that of the Noms, only one was a toxic. The other two where crazy sure, but not toxic. (one wasn't even awakened, and other, by the rules of the day as an adept couldn't be toxic. Only Shamans could be corrupted and turned toxic by the rules of the system back then)
So what you had was, by the admittance of the writers, was toxic death cult lead by one of the most powerful shamans of the age, toxic or no, With a unique power structure that couldn't exist anywhere else. And was probably held together by the Massive power and personality of a single leader - who
if I had to guess, probably built an Initiation circle with the other toxic members.
To this conclusion, I point to to what exactly they where trying to do:
Summon and bind massively powerful Storm Spirits to plunge the major cities into an unnatural, localized "winter"
Turn hidden nuclear weapons through unknown metamagics into "Magical EMPs" to fully burn out the matrix infrastructure and destroy the matrix forever (The Virus was PAX's idea, not Winternight. They never trusted it to work).
That's some serious mojo to sling, And Initiation Circles gain advantages to Ritual castings, not to mention cheaper initiation costs.... At the price of compelled loyalty through Geasa...
(But that's speculation based on years of reading and digesting and talking about Winternight...)
And, None of this have any bearing on your character

We need to know exactly what type of game this is going to be, otherwise you can't prepare properly.
As I tried to point out in my first post, These types of interactions generally don't go over well in a mixed game (where only one person is playing a Toxic/blood mage/invested/insect/infected type.) And in a game where everyone is playing as "malignant" arch-type (see list previous), you have different concerns.
Generally at character creation you are not allowed to initiate so, why talk about metamagics... IS he allowing you to Initiate at play? Is he giving you an alotted karma amount?
Are you using straight Priority? Sumto10? Karma buy?
DETAILS MAN! WE NEEDS THEM!
Edit: Threats was a 2e not a 3e book.