After reading through Chaos to Harmony at supersonic speed by Glimpse the hedgehog I had an idea to do a fanfic similar to it a sonic MLP crossover, I planned to have this after what had happened in Glimpse's but a different outcome where the events after where forgotten by everyone in ponyville and Sonic and Glimpse went home, I hope you don't mind Glimpse for making small references to your OC.
Harmonic Chaos chapter 1: an unexpected world
"Get back here Eggman!" Sonic yells at the fat scientist fleeing in his Eggmobile with a canister of animals in the Eggmobile's mechanical arm. Next to sonic was Rage who was helping Sonic after Eggman swiped the emeralds from under his nose in the middle of the night.
"You can't catch me Sonic!" Eggman laughs taunting the blue hedgehog who looked at Rage.
Rage replied with a grin "I'm on it!" he says picking up speed to get under the eggmobile. Rage charges a Chaos Spear and fires it right at eggman knocking the canister of animals out of the hand and breaking one of the jets.
"No matter… I have the other place I can work with…" Eggman complains pushing a button, then on the pathway bellow where Sonic and Rage were pursuing the scientist a small portal opens, "NO! not down there!" Eggman yells
Rage and Sonic try and stop themselves but a tree branch flings them into the portal and it closes behind them both of them fell and were knocked out from a small fall,
Rage wakes up in a large room filled with books, "Ugh… What's happening…" Rage groans opening his eyes he looks next to him hoping to see Sonic, instead he saw a purple pony next to him
"Are you okay?" she asks in a worried tone "I found you and a blue… thing?" she pauses trying not to be offensive "out in the middle of the Everfree forest out cold... Im Twilight Sparkle"
"Blue thing…?" Rage slowly sits up and rubs his head but to his surprise he had no hands "Gah! What in chaos?!" he looks at the flat hoof and notices his feet were just the same. Rage tries to stand up on the four hooves and had little trouble 'just think like I'm crawling' he tells himself in his head
"Gah! My chili dog!" Sonic snaps awake and looks around to see Twilight looking at him and he just stayed speechless
"Sonic?" Rage asks looking to see that he was still normal, Rage got a dumbfounded look back from Sonic,
"Rage is that you?" he asks, Rage nods in response. "Did Eggman do this to you?"
Rage's eyes light up at the thought of what had happened "Wait where are the Chaos Emeralds?!" he looks around franticly
"I think I will leave you two alone to sort this out…" Twilight stammers closing the door to the room
"Eggman…" Sonic sighs "he sent us here back to Equestria just like he did a while back with me and Glimpse… but Rage who is it that you changed into a pony and I'm still myself?" Sonic looks at Rage trying to make sense of everything
"I wounder if it's due to my connection with other worlds…" Rage says to himself "Do you have the Chaos emeralds?" he asks Sonic
"No, don't you?" Sonic asks Rage who turns around again and Sonic notices what looked like the chaos emeralds on Rage's left flank "Uh… Rage I think there in you…" Sonic comments slowly "In that Cutie Mark…"
"What?" Rage looks at his left side and there they were all seven emeralds embedded like a patch of fur on him, "A Cutie Mark?" Rage turns to Sonic "What is it that your not telling me?" he asks suspicious
"It's about that one adventure I never speak of…" Sonic sighs, "This is where it all took place… did you see the sparkles on that pony's side?" Rage nods in response "That a cutie mark it represents her. And I guess as the guardian of Chaos the emeralds used themselves as your cutie mark to adapt to Equestria."
Rage stands up and walks out to meet Twilight who was waiting there for an explanation,
"Twilight if I recall, This may sound weird but me and my friend here are not from here, we are from Mobius I have to apologize for all of this…" Rage hopes she would understand and not find him crazy
"Mobius?" Twilight looks at him "Like the one in my book the planet that's home to the seven emeralds that act like the elements of harmony?"
"Uh… yeah that what this is" Rage turns his left side to her and she looks at he mark on his side
"I see… I think Princess Celestia would like to know of this…" Twilight signals Rage to follow her
"Wait! I need to get back to Mobius!" Rage objects to the purple pony
"I don't think that will be possible for a while…" Twilight sighs "With the Northern Tundra under rule by Discord all outerworld transports were cut… you're trapped here until he is gone…" Twilight starts shoving Rage to move him "Now you must see Princess Celestia!" she insists pushing him through a set of doors into a large hallway. She leads him to a set of doors with two ponies at watch, they open the doors and Rage looks at the size of the room with the two princesses at the other end of the room.
"Twilight what troubles you?" Luna asks the purple pony
"…Rage care to explain?" she asks Rage who looks back at her with surprise, eventually he gets the courage to explain
"Well…" he sighs "Me and my friend were sent here by accident from our world and seemed to have ended up here. I… am sorry for all this trouble this might have caused." Rage dips his head trying not to get on the bad side of anyone, if there was one thing he knew it was different planets had different people with different abilities.
"This is troubling…" Celestia sighs "I'm not troubled by this at all what troubles me is the fact that you have to be stuck here… so I should be the one apologizing not you… but if you come from Mobius you must know that your normal name will not work around here if you want to fit in without any… problems I suggest you accustom one like ours… Twilight please Take Rage to Ponyville and get him settled… I will keep Sonic here so he does not frighten anypony." Twiligh nods and leads Rage to the train to take him to Ponyville
The two arrive and Twilight takes him into the Library before asking him a question "I need to know what you did back on Mobius, this way I can think of a fitting name for you here,"
"I guarded the Chaos Emeralds why does that have anything to do with this?" Rage asks
"In Equestria names include a personal trait and then your birth name after you get a cutie mark that is…" Twilight pauses "I think the only one that will fit you that you'd like is Chaotic Rage…"
"Works for me." Rage shrugs, before a dark red pony with a grey mane walks down the stairs with Spike
"Twilight what the status on the new pony you found?" he asks
"Oh Lunar Relic this is Chaotic Rage he's the new pony" Twilight looks at the pony surprised to see him
Lunar Relic walks up to Rage and greets him "Names Lunar Relic, just call me Lunar. Please to meet ya Chaotic Rage!"
"Please call me Rage," Rage greets him in response "Now then Twilight I need to know what's going on here exactly… I will help you guys all that I can while I'm waiting this out."
To be continued…