I must admit, it never occurred to me that someone who wasn't familiar with the Harry Potter books might want to read Alternity. But it seems there are some! In order to make the game more comprehensible to those people, then, I wanted to write a short introduction to Alternity that will help folks who haven't read Harry Potter get on their feet. Reading this, then moving on to the first Previously On Alternity entry and so on, ought to bring you up to speed.
Alternity is set beginning in 1991 and continuing in real time from there. The world in which Alternity is set is an alternate version of our world. Here, magic is real. A small percentage of the population is magical. It's unclear whether magic is passed down in families or not - it seems likely that it's genetically determined, because if you come from a magical family, you're likely to have magic too. People who come from a magical family but don't have magic are called "squibs." People who don't have magic are called "Muggles." People who have magic, but come from a Muggle family are called "Muggle-borns." People who are of mixed magical and Muggle heritage are called "halfbloods." People of pure magical heritage are called "purebloods."
In the Alternity world, the magical community lived separate from but parallel to the Muggle world until the year 1981, governed by their own set of agencies and so forth. (In the UK, the governing bodies were called the Ministry of Magic and the Wizengamot.) They kept themselves secret from the Muggle world. In 1981, a dictator known as Lord Voldemort seized power over the UK in a violent coup. Lord Voldemort made magic public knowledge when he took over both magical and Muggle governments. Lord Voldemort was an extremist who believed that Muggles were inferior, including Muggle-born witches and wizards. Therefore, he instituted a program by which Muggles were subdued in a number of ways, including keeping some in large labor camps. Muggle-born wizards who were young enough to be trainable became personal servants to purebloods and trustworthy halfbloods. He also created an enormous magical barrier (a "ward") over the whole of the United Kingdom, preventing people from entering or leaving except through small, heavily-guarded ports and protecting the nation from Muggle weaponry (whether conventional or unconventional). Finally, he instigated various public works projects, the largest of which was the creation of "New London," that is, the conversion of London from a place suitable for Muggle life to a place suitable for magical life. Lord Voldemort slowly moved away from the image of a revolutionary dictator and has begun calling himself the Lord Protector.
The most prominent school for young magic-users in the UK is called Hogwarts School of Witchcraft and Wizardry. There, students learn such subjects as Potions, Transfiguration, Charms, Astronomy, Ancient Runes, Divination, and more. Hogwarts is divided into four Houses based on primary personality traits: Gryffindor (brave), Ravenclaw (clever), Hufflepuff (loyal), and Slytherin (cunning). Lord Voldemort was in Slytherin, and many Order of the Phoenix members were in Gryffindor, but this is not a hard and fast rule. The four Houses play sport against each other and compete for who gets the most House points (given for merits, taken away for demerits). The primary sport is called Quidditch, which is somewhat but not entirely like football on flying broomsticks.
Hogwarts is where most of our story takes place. Its former headmaster, Albus Dumbledore, was a prominent critic of Lord Voldemort's rise to power. Upon Lord Voldemort's rise to power, Dumbledore fled the UK, leaving his Deputy Headmistress Minerva McGonagall in charge both of the school and the resistance to Lord Voldemort within the UK. This resistance is called the "Order of the Phoenix," named after Dumbledore's companion animal, a phoenix named Fawkes. McGonagall, however, had to kowtow to Lord Voldemort in order to remain in control of Hogwarts. Therefore, she is now a double agent - both the head of the Order of the Phoenix and a member of Lord Voldemort's closest inner circle, the Death Eaters.
Complicating all this, of course, is the fact that Lord Voldemort is widely known to be essentially immortal. What most people don't know is the details of why. A prophecy was uttered that ties Lord Voldemort's fate to the fate of a young boy (an infant at the time) named Harry Potter, the child of two members of the Order of the Phoenix. In fact, the first action of Voldemort's coup was to take Harry into custody. Harry grew up believing himself to be Lord Voldemort's son, Harry Marvolo. Our story starts when Harry begins his first year at Hogwarts - and begins to learn about the real state of the world.
Important characters that haven't been covered yet:
Lucius Malfoy - an important Death Eater. Has a son, Draco, who was raised side by side with Harry as a foster-brother. His wife's name is Narcissa, and she's a member of the important Black family of Death Eaters (covered below). He is responsible for an old friend's daughter, Pansy Parkinson, as well (her father is dead and her mother alcoholic).
James and Lily Potter - the true parents of Harry Marvolo and members of the Order of the Phoenix. James and Lily were both killed in the coup in 1981. Lily was a Muggle-born; her sister, Petunia, and Harry's cousin Dudley are lost somewhere in the shuffle of Muggle camps.
Sirius Black - James Potter's best friend from school, Sirius rejected his pureblood, Lord Voldemort-following family to become a member of the Order of the Phoenix. Sirius is now an Order agent on the Continent, trying to figure out how to smuggle goods in.
Remus Lupin - Another of James and Lily Potter's friends, Remus is a werewolf. Because werewolves are Lord Voldemort's allies (for the most part), and because he is suspected of having informed Lord Voldemort where James and Lily are, Remus is not trusted by the Order of the Phoenix. In fact, however, he remains loyal to James' and Lily's memories. He is Hogwarts' groundskeeper.
Bellatrix Lestrange (née Black) - Sirius' cousin, she is a prominent Death Eater and a little bit off her rocker. She is in charge of law enforcement in the new regime. Her husband is Rodolphus and their child, a year younger than Harry, Hydra.
Frank and Alice Longbottom - members of the Order of the Phoenix, they left their children Neville and Evelyn to run a sanctuary for Muggle-born magical children on a remote island, Moddey Dhoo. They frequently find themselves dodging Death Eaters in order to spirit Muggle-born babies away.
the Weasley family - members of the Order of the Phoenix, they have many children. Two, Bill and Charlie, are grown. Four are still at school: Percy, Fred, George, Ron. The youngest, Ginevra (Ginny), is at home. The father, Arthur, works to administrate the Muggle camps and often tips the Order of the Phoenix off to bad situations there. The mother, Molly, is a housewife who has to make ends meet on a very tight budget.
Hermione Granger is a Muggle-born slave assigned to Hogwarts to work in the library, tending books that are too complex or human-specific for house-elves to deal with. She's the same age as Harry.
Terry Boot is also a Muggle-born slave at Hogwarts, Harry's age, but he is the personal servant of the abusive Alecto & Amycus Carrow, two professors.
Dennis Creevey is a third Muggle-born slave at Hogwarts, younger than Harry, but assigned to Harry as his personal servant.
assorted other students, Death Eaters, Order of the Phoenix members, and staff - there are plenty of other characters in the game, some of whom become quite important, so get to reading!