Sonic Boom: Beyond the Black Horizon is an in-progress Alternate Universe fic by General-RADIX that can be read here
. Planning began before its canon basis, Sonic Boom: Rise of Lyric, was released; as a direct result, there is very little overlap between the two works.
Zephyros Veloi Sonic, a young man who lives a solitary life in the woods and has never met anyone or anything that wasn't trying to kill him, follows his nemesis Dr. Ivo “Eggman” Robotnik back to one of his many covert operations and ends up assisting a team of amateur archaeologists who had gone to said operation to blow it up. Said team—comprised of Amy Rose (leader and translator), Knuckles the Echidna (photographer), and Miles “Tails” Prower (mechanic and pilot)—wants him to help them disable a powerful lost artifact called the “Omnivastator”, which Eggman also has his eye on.
While he does eventually agree to go along, Sonic is rather resistant to the idea of working with others and barely knows how to socialize; his new teammates are determined to get him to open up and refuse to let him rush into danger alone, whether Sonic is more familiar with the Doctor than they are or not.
As Sonic suspects of their main goal, taking care of the Omnivastator won't be as easy as Amy and her assistants hope it'll be—for one, the “artifact” is actually a snake-like cyborg, Lyric, who believes that Sonic was the one who sealed him off despite the fact that he was cryogenically-frozen a millennium ago (a fact that Lyric himself was not initially aware of). The team now has another enemy to deal with as they attempt to keep Eggman from acquiring the revered Holy Crystals and to just make sense of things, armed with little more than their recently-discovered Enerbeams.
Beyond the Black Horizon contains examples of:
- Alternate Universe
- Art Evolution: Carried over as-is from the canon Boom series—for the most part; Sonic and Amy's heights are reversed.
- Big Bad Duumvirate: Eggman and Lyric, as per the canon game; their team-up occurs much earlier and is more even-handed, due in part to Eggman making some effort to help Lyric instead of subjugate him.
- Big Creepy-Crawlies: Sonic hunts the giant Mobini caterpillars that live in parts of the forest.
- Bleak Level: For a peninsula that's mostly comprised of jungle, Favonius is oddly lifeless. All the colours are a shade removed from what they're supposed to be, there's no evidence of any lurking wildlife, and the only major landmarks are a crumbling, abandoned village and Terminus.
- Border Patrol: Wander too deeply into the forest, and risk getting stung to death by giant wasps. They're part of the reason why Sonic still hasn't traveled to that giant amethyst spire that's within view of his house.
- Down the Drain: The Cascade Temple underwent a forced partial conversion into a water filtration plant, necessitated by the heavy pollution that plagued the area in the past; Sonic and Amy don't get to see much of the original architecture.
- Dramatic Irony: Lyric has been imprisoned for a thousand years. His primary concern upon release is regrouping with his fellow World-Wreckers.
- Even Evil Has Loved Ones: Sonic learns this the hard way.
- Foregone Conclusion: That the “Omnivastator” turns out to be Lyric is not a spoiler.
- Foreshadowing: The final obstacle between Sonic and Knuckles and the end of the Pit is a giant drilling robot that Sonic suspects was not built by Eggman.
- Implacable Man: Nothing can deter Leviathan, Guardian of the Cascade Temple, from chasing down and crushing intruders. It may take them a bit to catch up, but catch up they shall.
- I Surrender, Suckers: When Sonic and Amy finally catch up to Eggman in the Cascade Temple, Sonic knocks him out of his hover vehicle and warns him not to give them any trouble. For a moment, it seems like Eggman might comply—then he starts strangling Sonic in mid-air and orders his Pawns to restrain the hedgehogs.
- Laser Blade: One of the functions of the Enerbeam. The length of the blade varies by user.
- Names to Run Away from Really Fast: Lyric's own team was nicknamed the World-Wreckers.
- Nice Job Breaking It, Hero: In his anger over Burroughs insulting Amy to her face, Sonic mentions Leviathan by name when he's not supposed to know that the Guardian even exists. As a direct consequence, Amy, Knuckles, and Tails are unceremoniously expelled from the Guild. Later on, the poor guy accidentally releases Lyric (albeit not in the exact same way he did canonically).
- No OSHA Compliance: As to be expected of Eggman, the Pit is not the safest place to work if you're not one of his robots.
- No Social Skills: Sonic has lived thirteen of his eighteen years with no friendly Mobian contact whatsoever, so naturally, when he finally encounters friendlies, he's a bit lost (in fact, he locks up and runs off, forcing Amy to track him down later). Even as he adjusts to interacting with Amy's group, there's a few things he doesn't quite get, like how handshakes work, or that startling people is not a good way to greet them.
- Obstructive Bureaucrat: Obtaining permits to dig in restricted areas is an arduous task as-is, but if your request gets forwarded to head Guildsman Burroughs, just abandon all hope.
- One-Handed Zweihänder: Lyric dual-wields a set of beam sabres that an ordinary Mobian would have difficulty swinging around with both hands. It helps that his suit essentially grants him superhuman upper-body strength.
- Ragnarök Proofing: Played with. No one's been in or out of Terminus for a whole millennium, but the overhead lights still work, albeit with much flickering (Amy speculates that they're powered by lesser crystals, which generally last a very long time). However, the Time Research Center's analog computer can't even handle one set of commands without finally breaking down—and with the computer goes all of the mechanisms that kept the cryo-stasis systems running.
- Scarf of Asskicking: Sonic's brown bandanna.
- Screw the Rules, I'm Doing What's Right!: Mayor Fink informs Burroughs that handing Amy, Knuckles, and Tails over to the Imperium (who Burroughs insists will execute the lot of them, Tails included), even though they broke some very important Guild rules, would be deeply inadvisable.
- Sealed Evil in a Can: In retaliation for attacking the people of Favonius, said people deep-froze Lyric.
- Servile Snarker: Of the many traits that Metal Sonic developed as a sentient being, the one that annoys Eggman the most is his "rotten attitude" that's similar to the original Sonic's; Metal has no qualms about rubbing in the Doctor's numerous failures and leaps of logic.
- Wild Wilderness: Sonic's house is located near the edge of a dense forest.
- Zerg Rush: What the Egg Pawns are programmed to do if they significantly outnumber their targets, according to Sonic.
