For nearly 1,000 years, Heaven and Hell have waged an endless war upon eachother. With no clear signs of ending- the rulers of each realm have come to a conclusion, war is pointless. Neither side was destined to win.
While truce was- difficult to process (Since "citizens" didn't exist, everyone went to war, except for medics who stayed back, but they still contributed) and it was... Odd for everyone to say the least, everyone was always on edge up until the truce. But after a hundred or so years, angels started to move to hell, and vice-versa. Some even fell in love with their new homes, and their inhabitants. It was beautiful to see them together, blues, yellows, whites, or reds, greens, and black. All colours were beautiful.
Although many demons and angels fell in love with eachother, none were able to conceive. It simply wasn't possible. Many were devastated, especially since adoption was rare.
Their DNA couldn't mix, like when you try mixing black and white, you may get grey, but not an even amount. So it wasn't quite right.
And the colours? Demons consisted of three colours and many shapes and forms, with powers to correspond, likewise with the angels.
Angels, they had gorgeous white feathered wings, luxurious white or blonde hair, and some even had halos, which were either white, blue, or yellow. However only high angels, archangels, and the leader of Heaven had halos. The halos and wings could be hidden using magic, when used correctly the wings would retreat into their backs, and their halos could become bracelets or simply vanish.
Angels could have a few powers, many excelled at healing, or light manipulation. However it was more common to have magic, which they could use to manipulate summons, spirits, or the elements.
On the other hand demons had black wings, sometimes with green or red. Their wings could be feathery, similar to the angels, and purely black. Or the wings could have scales, and look more like that of a dragons, in which case they'd appear with a secondary colour of either green or red for the webbing. Instead of halos the demons had horns, curly horns, straight horns, curved horns... In all cases but a handful, they were black (red for high demons). Demons are brunette, with either light brown, or dark brown hair (with the appearance of black). And unique to demons, they had tails, with shapes on the ends. The tail itself was always black, but the tips could be red, green, or remain black (the cause is unknown, however it is assumed to be from one of two reasons, either genetics, or power level).
Demons can also use magic, shadow manipulation, and finally curses, they are not exempt from having healing powers, but it is extremely rare and unlikely.
While both angels and demons are eternally youthful, they still can be killed, although it is difficult. Another noteworthy fact is that they can never get stronger. They will forever be the same strength as they were when they awaken.
Awakening is simple, upon reaching 14 years old the demon, or angel, gets one of their growth spurts (which occur at ages 2, 6, 10, 14, and 20) and awaken their powers. They do not grow or age inbetween growth spurts.