Shadowline (also referred to as The Shadowline Saga) is the shared world setting for a line of comic books published by the Epic Comics imprint of Marvel Comics.
In this world, another species - the Shadow Dwellers - developed alongside humans. Shadow Dwellers have a wide range of appearances and powers, and don't age unless they choose to have children.
In modern times, humans are largely unaware of this second race's existence. And then some Shadow Dwellers decide to change that…
The line was initially composed of three books, each published bi-monthly:
- Doctor Zero is the oldest and most powerful of the Shadow Dwellers, clever, ruthless and manipulative. In modern times, he cynically crafted a costumed superhero identity for himself - the titular Doctor Zero - and uses it to announce his presence to the world.
- Power Line are two young Shadow Dwellers who sincerely want to help people and try to become more traditional superheroes.
- St. George follows Michael Devlin, the latest knight of the titular order. Michael's human, but the monks of the order, who crafted his armor and lance, are Shadow Dwellers. If his faith is true, Michael might find the power he needs to defeat the order's ancient enemy and save the world. If he can't find that focus, using the armor may destroy him.
The three books were cancelled together due to low sales, at which point a fourth was launched:
- Critical Mass is a prestige format Anthology Comic limited series, serving as a Crossover Finale for the previous Shadowline titles. It alternates between chapters starring the different protagonists.
After the Shadowline books ceased publishing, a version of St. George antagonist Shreck reappeared in the Marvel Universe as the star of Terror Inc.. Another, slightly different, version appeared in two "explicit content" miniseries from the Marvel MAX imprint (Terror, Inc. (MAX) and Terror, Inc. - Apocalypse Soon).
Despite this, the continuity status of the Shadowline setting itself was left vague until 2005, when the Official Handbook of the Marvel Universe: Alternate Universes connected it to the wider Marvel Universe.
Secret Wars (2015), one of Marvel's Crisis Crossovers, later featured versions of Doctor Zero and St. George, with the characters playing minor roles in the event's spin-off Squadron Sinister series.
The Shadowline setting contains the following tropes:''
- The Ageless: The general rule for Shadow Dwellers, but averted once the Immortal Procreation Clause kicks in. A Shadow Dweller who has children starts aging again.
- All Deaths Final: The setting doesn't use magic or other means of resurrection. Some characters are very hard to kill and others can reanimate corpses. But dead is actually dead.
- All There in the Manual: Shadowline was initially presented as a shared universe with no connection to the alternate worlds of the existing Marvel Universe. The Official Handbook of the Marvel Universe: Alternate Universes then confirmed that it was actually part of that multiverse.
- Breakout Villain: Shreck, who was reinvented in both the Marvel Universe (initially via Terror Inc., which was followed by appearances in Deadpool and elsewhere) and Marvel MAX (via Terror, Inc. (MAX) and its sequel Terror, Inc. - Apocalypse Soon) after the Shadowline books ended.
- Canon Welding: The Official Handbook of the Marvel Universe: Alternate Universes eventually connected the Shadowline world into the Marvel Universe, labelling it as Earth-88194.
- Capepunk: The general style of the setting. Heroes are complicated and there are many shades of grey.
- Immortal Procreation Clause: Shadow Dwellers are normally The Ageless, but they start aging if they become parents.
- Wainscot Society: The Shadows live in their own hidden society alongside humans.
