Mike’s favourite colour is pink, Rachel’s is plum - sunflower yellow comes in a close second.
Mike’s strengths lie in infectious enthusiasm and zeal for life, an uncanny ability to befriend, or at least endear himself to people, and a keenly curious mind. He’s still in the process of growing, but he’s adapting quickly to the new world he’s in. Rachel has a long and full lifetime of experiences - good, and bad - to draw from, and she does when it comes to advice or how to conduct herself. She’s made her mistakes; she’s done a good job of learning from them.
Conversely, Mike is a bit naive and ignorant in regards to a lot of aspects of human culture still, and the gaps in understanding that he has can lead to anywhere from faux pas to assumptions that can put him in real danger; he assumes we work logically. We do not. (That assumption is being whittled away, albeit slowly.) He also is not familiar with fighting the way most Devils are; he is strong (Boy can carry over a ton if he puts his back into it,) but put him against someone who knows what they’re doing, and he’ll lose - even if that someone’s human. Rachel has ghosts standing behind her, old vices that won’t let her move on, though she’s gotten past the worst parts of recovery. She keeps a lot of secrets, and holds on tight to compassion, preferring not to let people past her outer layer. She also does tend to believe, as she’s over a thousand years old, that she knows how to handle things.
Devils don’t really keep secrets of their own; any they do have are political and belong to the court. They’re schemers, and can’t really reveal the inner workings of Hell to anyone, and both of them do know whether or not someone is damned when they meet them - and they have two damned cousins for whom they know what fate awaits them when time eventually comes to collect.
Enemies are, again, more racial than personal; but for very good reason. Hell is a culture at war, and demons would relish the chance to take either of their lives eagerly to set back their father’s efforts to keep the Abyss from overflowing onto the topside planes. All of Hell is an engine whose sole purpose is to keep Demons off the worlds of the mortal races, and as a result, demons are their top aggressors and enemies, even as individuals.
Honestly, the most noticable thing about either Mike or Rachel is that... well, they’re Devils.
But individually? Mike’s either the big yellow eyes, blond hair that he’s dyed with streaks of black and pink, it might be his clothes if he’s wearing something particularly eye-catching; his wardrobe ranges from skinny teenage boy in silk screens to adorable sweaters and skirts he found, the big cheesy grins that show off a mouth full of nothing but triangular teeth being pulled into alignment by pink braces, how ridiculously long his tail, fingers and toes are or all the piercings he has, depends on what sort of things you prioritize visually.
Rachel, on the other hand - her clothes are eye catching to, but in a ‘look at me, I’m gorgeous’ way. Second skin trousers, shirts that don’t have a back at all - she’s winged, after all, and her wings are much bigger than her brother’s - and often dip low in the front. Miniskirts. She has hooves, not feet, and her calves are furred up to lava-like scales at her knees. Might be her eyes, which have grey around her gold irises instead of white, or that her lips and tongue are grey, that she only has two taloned fingers and a thumb on each hand, or the blonde streak in her otherwise black hair. Again, it depends on what you focus on first.
