Sergius O’Shaugnessy is really Denny O'Neil, as he was a big Mailer fan. So much so that he tried to live up to the whole hard living and drinking Irishman, which only resulted in losing chunks of his life.
Black Brother(which by the way never continued despite what the corner title says) was published in Savage Tales #1, and was one of the many experiments Marvel tried in the 1970'. Some of them, like Man-Thing, were phenomenally successful. This, not so much. It certainty has some interesting ideas, despite the somewhat pretentious foreword, but it never quite gels. Nonetheless, Gene Colan is one of my favorite artists, and he is on top of his game here.