After who-know-how-many months, and with some excellent help from Mirustal, I have finally gotten a complete OC, backstory and all!
So without further ado...
General Traits: Name: Slate Grey Gender: Male Species: Unicorn Occupation: Traveler, wanderer and problem solver. Appearance: A Slate Grey coat color with longer tufts of hair on his fetlocks and chin, greenish-grey eyes and a long, slightly unkempt dark brown mane. Unlike most ponies his tail looks like a lions tail with a brown-haired tuft at the end, his hooves are cloven like a goat's and his horn is a bit longer and thinner than normal. Overall he is fairly tall but slender. He wears a pair of round glasses and is often seen with an assortment of saddlebags, pockets and other traveler's gear. His cutie mark consist of three black hoof-prints.
Story: Slate Grey comes from a small village, located along a river and in a great fungal forest. Not many in Equestria have heard of the place as it is in fact on a far away continent. Far away enough that there the story of princesses raising the sun and moon was a mere myth contending with other myths about the celestial bodies, like the one that claims invisible gods move the heavens and even a particularly outlandish one that suggests all the heavenly bodies circle one another in an endless void! Growing up Slate quickly got a reputation for being devilishly curious. He did not just ask where the river's water goes, where the forest stops or who raises the sun and moon but tried to go there and find out for himself. He would spend much of his time getting into trouble exploring the forest's lakes, valleys and shroom swamps (some of the smelliest in the known world!) and if not that could spend hours listening to the stories of elder ponies. Much to the bafflement of the other foals who usually fell asleep in the first minutes. The village had a school that taught the basics of worldly knowledge but Slate quickly grew bored of the schoolbooks with their dry, factual and lifeless stories. Much rather he heard of these places from somepony who had been there, about how the food was, what brought them there and who made for good friends. Those were real stories! School did teach some useful things however. Basic magic, languages, reading and mathematics supplemented with teachings in alchemy from Slate's parents, who were both potion makers by trade. As Slate got older, he got unrulier. Skipped school to run about the forest, went on secret trips to the only other nearby village (and its tavern) and eventually he payed an old barge-griffin to take him down the river. Once they reached the edge of the forest, Slate knew he was meant to travel and had the cutie-mark to prove it.
After that he spent his days on the move. Not far at first, and he had to blow a shameful retreat back home a few times, but eventually he learned the difficult trade of traveling, exploring, navigating and doing all sorts of odd jobs to pay for his expenses. He got to see where the forest ends, where the river flows into the ocean and, eventually, where they raise the sun and moon. Along the way he learned of plenty languages, foods, cultural habits, spells, herbs and potions. All of which certainly helps doing odd jobs, and a decent pay. He may be an outdoors pony, but if he still prefers a nice bed and plenty of the local food and drink to go with it! Despite looking like a bit of a rogue, he is generally a fair and honest sort. He makes sure he is payed enough, but no more than fair. He does not always tell the whole story, but would only lie if he really had to. He can defend himself, but avoids violence as much as he can. After all fighter's stories never really have a good ending.
When he goes somewhere, he does not take tourist tours. He learns of the place beforehand, travels there on hoof or if needed hitches a ride with another cargo ship (which became a habit, and is also quite economic) and makes camp in a quiet place nearby. He then walks into town to wherever the locals go to eat and drink and asks around. How things are going, how the harvest is coming along, why the mayor dresses like that, what that dish with the icky black thingies is, that sort of thing. Eventually there is always somepony, or 'someone' as plenty of towns are inhabited by folk that are no ponies, who needs help with something. That's where he plies his various trades. Potions that soothe migraines, spells that root out moles, just simple farm work and at some point how to build a functioning catapult. Slate spends most of his earnings on food, warm beds and trinkets which he stores in a seemingly bottomless saddlebag and eventually moves on. He could stay in a place for just a couple weeks or several years, depending on how long a place can hold his interest and how long his work takes to finish.
Nobody knows exactly how long he has been doing this and when asked he claims he 'lost track of that a while ago'.
Addendum That got longer than I thought! Wonder if anyone read this far... Also for who is wondering, Slate's appearance is based of the medieval unicorn. They looked much liked one-horned goats with lion tails. No pictures yet, I can't exactly draw, so my ponymaker profile picture and this vivid description will have to do for now. If there are any typos, wrongdoings against equinity or just suggestions, do let me know!
2015-06-10: Revised some details and removed some typos.