Publisher: Epic (Marvel) Comics (1988-1990)
Includes: Marvel Age #62, Doctor Zero #1-8, , St. George #1-8, Power Line #1-8 and Critical Mass #1-7
Clipped from Wikipedia: The Shadowline Saga is a comic book imprint from Epic Comics that was created and edited by Archie Goodwin. The Shadowline Saga was Marvel's first attempt at creating a mature-themed line of superhero comics. Further, it was the first line produced by Epic Comics utilizing a pre-conceived shared universe concept.
Critical Mass Anthology - Doctor Zero, Power Line, and St. George #9 - 13 were supposed to be part of The Shadowline Saga "Critical Mass" Crossover. Due to poor sales, Epic cancelled the three Shadowline series and published the story in an anthology format as the Critical Mass limited series.
Clipped from Marvel1980's: From Goodwin’s Epic-Grams in May 1988:
“My original vision of Epic didn’t really include doing super hero comics. I felt we were around to break some new and different ground and Marvel had already proven that super hero comics could be done successfully and well. (…) And sometime in the midst of all this, I began to toy with the notion of the Shadow Line Saga. I thought I had it all reasonably well worked out in my head in late summer of ’86. Then I began to write and it was February of ’87 before the bible was done on the series. But I liked what I had. Super heroes I could live with … and enjoy."