1985’s Crisis on Infinite Earths was a housecleaning intended to sort out DC’s continuity problems once and for all. It had the opposite effect: rather than simplify things it made things stupidly complicated. The Legion of Super-Heroes, a group of powerful teens living 1000 years in the future, formed their team after being inspired by the adventures of Superboy, a young Smallville-based Clark Kent. But in post-Crisis continuity, Clark Kent didn’t put on a cape and costume until he was an adult living in Metropolis, meaning Superboy never existed, meaning the Legion should’ve never come to be. Except there they were, so how were writers supposed to reconcile their pre-Crisis origin with the new post-Crisis DCU?
Writers Paul Levitz and John Byrne attempted to set things straight in 1987’s “The Greatest Hero of Them All” storyline, which explained that Legion villain Time Trapper, aware of the continuity changes that resulted from Crisis and wanting the Legion’s history to remain intact, created a pocket universe in which an alternate-reality Superboy could exist. This Superboy could function as the catalyst for the Legion’s creation, and the Legion could still travel back in time and adventure with the young (pocket universe) Clark Kent.
Another problem created by the original Crisis: Supergirl died and was wiped from continuity, thereby eliminating a character people didn’t even realize they liked until her untimely demise. In his introduction to the Crisis on Infinite Earths Hardcover/TPB, Marv Wolfman writes that a lot of readers told him that “Beyond the Silent Night” from Crisis on Infinite Earths #7, in which Kara sacrifices her life fighting the Anti-Monitor, was the best Supergirl story they’d ever read. He also explains why Superman’s background needed to change: “Before Crisis, it seemed that half of Krypton survived its explosion. We had Superman, Supergirl, Krypto, the Phantom Zone criminals, the bottle city of Kandor and many others. Our goal was to make Superman unique. We went back to his origin and made Kal-El the only survivor of Krypton. That, sadly, was why Supergirl had to die.”
Two years after Crisis ended, John Byrne found a way to revive a beloved character without breaking any of the new continuity rules: introduce her as a protoplasmic shape-shifter from the pocket universe created by the Time Trapper. Her origin is recapped in the opening pages of Action Comics #677:
Matrix (named after her body’s protoplasmic material) figured heavily into two notable story arcs after her introduction: “The Supergirl Saga” in which Matrix recruits Superman to fight three escaped Phantom Zone criminals and pocket-universe Earth gets destroyed in the process, and “Panic in the Sky,” in which Superman fends off a potential invasion from Braniac.
She would later be featured prominently throughout the immensely popular “Death of Superman,” “Funeral for a Friend,” and “Reign of the Supermen” storylines, even getting her own above-the-title credit on Action Comics #686:
A significant part of Matrix Supergirl’s story was that she was in love with Lex Luthor’s son, a red-haired, bearded gentleman who ended up being the actual Luthor in disguise. To Superman’s chagrin, the two enjoyed a lengthy romance until the 1994 Supergirl four-issue miniseries, in which things end up about exactly as you’d expect:
She also spent the better part of a year in New Titans, stopped by Hawaii to guilt-trip Conner Kent in Superboy, and received an annual feature in Showcase:
Matrix was an interesting way to re-introduce the Supergirl character to modern audiences without breaking any of the rules set out by post-Crisis continuity. She was, in many ways, more alien than Superman: he was a flesh-and-blood being from the planet Krypton who gained powers under earth’s yellow sun, whereas she was a mass of shifting purple slime created in a lab and given a powers and a human-like form by a scientist; Superman had a family and knew the rich history of Krypton, whereas Matrix had no childhood and her universe had been destroyed.