- Ascended Fanon:
- Technically true of all games, as the creators have said that every game played is canon to the storyline, representing one of the uncountable timelines in the multiverse.
- In a more specific sense, One player's fan fiction about the Wraith's final battle with Spite proved popular enough that it inspired one of the video game's Weekly One-Shot challenges. Subverted, as the game's writers revealed Wraith was not in fact the person who finished Spite off... but then again not subverted, with the above ruling that all games are canon.
- The Cameo: Heroes will occasionally pop up in other unrelated works from Greater than Games, like Bottom of the Ninth or Lazer Ryderz.
- Defictionalization: Variation — there are no actual Sentinels Comics comic books, except for the Freedom Four Annual No. 1 on the game's website. But the fandom has been clamoring for comic books in the universe for some time, and got their wish as one of the stretch goals for the OblivAeon Kickstarter was to produce Freedom Five Annual No. 30, which tells the story of OblivAeon's arrival.
- Development Gag: The game's creators have said repeatedly that Absolute Zero was heavily reworked from his original conception, going from essentially "Ra with an ice gun instead of a fire staff" to his current design. During the Absolute Zero episode of the Sentinels podcast, Adam and Christopher revealed that, in the fictitious world of Sentinels Comics, there was an unrelated Golden Age hero named Henry Goodman who took the alias Absolute Zero to fight Nazis with an ice gun and co-founded the original Freedom Four before being forgotten due to a lack of popularity in-universe (and later replaced on the rebooted Freedom Five by the current Absolute Zero, Ryan Frost). Later in the podcast episode, Adam and Christopher state that a reference to the origins of the character.
- Fan Nickname:
- Omnitron is called Omni for short.
- Like Omnitron, Omnitron-X is called Omni, Omni-X, or simply OX for short.
- The Legacies: Legs for Legacy, Baby Legacy for Young Legacy, Angry Paul for Iron Legacy, and Old Legs for Greatest Legacy.
- Greatest Legacy has also gained the nickname Grandpa Legacy from both the creators and fanbase alike.
- Expatriette is shorted to Expat.
- Turducken, for the rare occasion when Naturalist is able to finagle all three of his form cards out at once.
- Omnitron's (the villain) variant, Cosmic Omnitron or Omnitron II is also known as Cosmitron.
- I Knew It!: At least half the forums called that Grand Warlord Voss was the tenth Scion of OblivAeon. Christopher and Adam had been getting letters about it since the start of the Letters Page podcast.
- Jossed: Word of God will occasionally step in to shoot down fan theories.
- One commonly accepted theory was that the Visionary came from the Iron Legacy future, spurred by Iron Legacy showing up on the art of one of her cards, with her referencing that the Legacy she knows is an "angrier man." The game's writers have said that while her Paul Parsons might be more hardened, he's not Iron Legacy.
- Another was that the Scholar's Philosopher Stone is an OblivAeon shard. This, too, was denied by Word of God.
- One of Us: Christopher and Adam are at least aware of TV Tropes, given that they namedrop several tropes on the Letters Page. Theyre also huge comic book nerds and love telling stories which is how they got into this whole card game thing in the first place.
- Promoted Fanboy: Played with. Richard Launius originally created Nightmist and the concept that would become Gloomweaver as a fan project, before the team at Greater Than Games took note and invited him to design both in collaboration with them. However, unlike many such Promoted Fanboys, Launius is already an accomplished tabletop game designer.
- What Could Have Been: Revenant and Setback were two of Adam Rebottaro's oldest ideas for a hero and a villain. However, once Kismet won a contest for a fan-submitted super-villain character, she was too perfect not to use as Setback's nemesis. Thus, despite his great importance to the overall storyline, Revenant never gets to appear in-person as anything more than a minion in one of the Vengeance decks.
- Absolute Zero was heavily reworked over time, starting off as just a scientist with a freeze ray (and a deck similar to Ra's, but ice-themed, according to Word of God). The creators decided this was too boring and tried to spice things up with a deeper, more-tragic backstory before just deciding to rebuild the idea from the ground up to make it more interesting. The "original" Absolute Zero remains in the game's fictional backstory as a Legacy Hero from World War II days replaced by the current version of the hero.
- The Wiki Rule: Maintained by some fans from the Greater Than Games forums.
- Word of God:
- The game's writers are active on its forums and regularly hold Q+A sessions on Twitch during art streams. Between these, they've put out a lot of information about the series, either new tidbits, or confirming fan speculation — e.g., that Setback and Expatriette are a couple and that Tachyon and The Matriarch are cousins.
- They also poke fun at it from time to time — in The Wraith's episode of the Letters Page podcast, they open by joking that the Wraith is actually three cats in a human suit before quipping, "That's canon, by the way," and moving on.
Trivia / Sentinels of the Multiverse