Malum Librum
A Malum Librum is a portal to an alien world disguised as a book. These worlds are commonly full of evil monsters, but also some good ones. Many great adventures have begun with an unwitting child stumbling upon one.
Poor Mikey found a Malum Librum last month and it took him two weeks to get home! He missed our date, too. But he brought back a souvenir for me: a lich's soul jar. So yeah, it's all good.