Mackie grew up in Cypress Hills, Brooklyn, mostly raised by his mother (Mackie's father died when the boy was just seven years old).
Editor
His first comics work was as an assistant editor for Mark Gruenwald in the mid-1980s. Promoted in early 1987 to Managing Editor of Special Projects, Mackie then oversaw many of Marvel's New Universe line. He also edited Avengers and Avengers West Coast while John Byrne worked on those titles. Early in Mackie's career, a running gag in Gruenwald's columns was that Mackie was a mysterious figure whose face no one at Marvel had ever seen.
Writer
Mackie first gained attention as a writer in 1990, when he and artist Javier Saltares launched a new Ghost Rider series for Marvel, revamping the character and introducing a new host, Danny Ketch. Mackie stayed on as Ghost Rider writer until issue #69 in 1996. Throughout Mackie's run of over five years, the Ghost Rider's ultimate origins and nature were never explained. A later writer, Ivan Velez, Jr., provided the character with a back-story shortly before the series was cancelled.
Shortly after the title's cancellation, Mackie had Ghost Rider guest star in Spider-Man and denounce Velez's origin story as being "lies" or at least incomplete. Since then, the true status of Ghost Rider/Noble Kale's origin and Dan Ketch's fate has yet to be determined.
Mackie was also the author of the cult classic Ghost Rider/Wolverine/Punisher team-up mini-series, Hearts Of Darkness (1991), and its follow up one-shot The Dark Design (1994). Both feature Ghost Rider's archenemy Blackheart as the primary villain. Focusing on those who walk the line between good and evil, Blackheart tries to corrupt Ghost Rider, Punisher, and Wolverine by promising them their fondest desires in an attempt to persuade the trio to assist Blackheart in destroying Mephisto. Blackheart ultimately fails in his attempt, and the group eventually follows Blackheart back into his own realm for a final confrontation.
In 1992, Mackie became a regular writer of Web of Spider-Man with #85. He would remain on various Spider-Man titles through the Clone Saga and beyond, finally leaving nine years later with The Amazing Spider-Man Vol. 2, #29 in April 2001.
Mackie also worked for the X-Men line, writing the spin-off title X-Factor from #115-149 (1995—1999) as well as its successor Mutant X title (1999). He also wrote several mini-series featuring Gambit, Wolverine, and Rogue.
In the Fall of 2009, Mackie teamed with Tom DeFalco to write a six issue miniseries entitled Spider-Man: Clone Saga, telling the story using Mackie's original notes for the 1990s crossover.
Spirits of Venom (in Ghost Rider/Blaze: Spirits of Vengeance (1992) #5-6 and Web of Spider-Man #95-96, December 1992 - January 1993, tpb, December 1993, ISBN 0785100091)
Venom: Nights of Vengeance (with Ron Lim, 4-issue mini-series, Marvel Comics, 1994)