Secret Magic in 1970 East Berlin

[ajardoor]

I've got this idea for a GURPS Cold War secret magic campaign.
It's set in East Berlin, the year is 1970.
The magic system is Effect-Shaping Book Rituals (see Chapter 5 of GURPS Thaumatology). Magic is both secret and illegal - the Communists officially deny magic is real but they treat magic as basically SUPER contraband.

PCs are all partisans, criminals, rogues, hedge witches, hunted men and possible undercover spies (for NATO or the Stasi) newly initiated into a spiritualist cult/crime gang of underground magicians in East Berlin. The cultists must undertake illegal black ops on behalf of their occult conspiracy under the nose of the Communist state...or secretly pursue their own hidden agenda...

Have you got any general suggestions? Advice? Cool historical things to include?
In particular, any ideas for a Ritual Book? Like, who it was written by (one should definitely be authored by Rasputin), what Rituals it has, the title, and so on?