1. Just as Tempest and Scorpan weren't ever exactly planning on being parents, Diamond wasn't exactly hopeful he'd ever have parents again. Ever since he was three, he'd been living in the same orphanage, passed up by different prospective parents day after day. He couldn't exactly blame them, however. He didn't really like to talk, hid his face away all the time, and didn't seem very interesting. Plus, everycreature knows that the older an orphan gets, the more difficult it is for them to be adopted. He was fully planning on sticking out the next three years with guaranteed food and bed, then striking out for his own life the moment he turned sixteen.
However, that all changed when Captain Tempest Berrytwist herself, and her strange (but kind) husband Scorpan, come for a visit the day after his thirteenth birthday. Being the mare that found him as a toddler, nearly burned to death, she'd been his most frequent visitor throughout his life. The gargoyle joins when he can, and despite his odd appearance, he loves to bring toys and gifts along and his jokes often manage to bring a smile to Diamond's face. Its then, as the three of them sit together eating some leftover cake, that Tempest asks if Diamond wants to come and live with her, and while he doesn't have to call her "mom" if he doesn't want, she'd love to be able to call him "son" once in awhile. He quietly accepts, then gives his new mother a kiss on the cheek. To this day, when he's not working, he still lives at his parent's cottage, and thinks of them as nothing else.
2. As illustrated by both his cutie mark, and funnily enough, his name (which Tempest gave him due to the color of his eyes), Diamond has a passion for gemstones and mining. While his specialty is spotting the different aspects of a giant gem deposit, he is also quite talented in helping his team find large loads of other much-needed resources, like copper and tin. He works primarily in the Canterlot diamond and sapphire mines, finding everything ranging from small gems to use as currency, to giant, beautiful rocks (one of which was refined to be Princess Cadence's anniversary pendant). He feels comfortable in his work — especially since others can't really judge his appearance in the dark.
Despite his mother and father's reassurance, those emotional scars that have been garnered over the years don't exactly fade quickly. Colts back at the orphanage weren't exactly the friendliest when it came to this scarred weirdo. So, he dedicates himself to his work, despite his parent's efforts to encourage him to get out a bit more — especially since the world is a bit different than it was, even when he was a kid. He makes occasional efforts to please them, but usually ends up returning to his mine. A worried Tempest talks to the expert, of course, and Princess Twilight suggests that it might be a good idea for the Ponyville mining team to "borrow" Diamond for a little while…
3. With that, he leaves Equest Leisure in Canterlot, packs his bag, and leaves on the Friendship Express for Ponyville. He has a minor inkling as to his mother's intentions, but sees this more as an opportunity to better train his eye to find emerald deposits. He plans on spending a few months here, perhaps visit old Trottingham for awhile, then go home. But, of course, this plan fell by the wayside as well. Heading to start scoping out his new venture, Diamond passes through a rolling, beautifully green meadow. While appreciating the beauty of the town's nature, the stallion very nearly runs into another creature…a blue mare with a long brown and blonde mane.
"Sorry 'bout that! Y'all were so quiet ah nearly didn't hear ya!"
Diamond, of course, is initially startled and irritated, thinking he was entirely alone. He didn't hear the other pony either. However, the mare doesn't seem exactly bothered. Before she can greet him, though, the socially inexperienced stallion shoves a hoof-full of gemstones at her, muttering his apologies for encroaching on her land. All she can respond with is a laugh and explaining she really doesn't need payment for passing through, while apologizing herself ("Ah can't see real well at all, an' like ah said, ah couldn' hear ya!"). They introduce themselves, and while Diamond declines Juniper's initial invite to dinner, he does eventually join her, her family, and her friends. He slowly becomes more comfortable living in the small town, and starts to discover that maybe other creatures aren't so bad…