With the UK version of the game, you get a free copy of the novella "Child of Caos". If you read this book you will find out exactly how the 2 games link up...
In short....
In DD you couldnt kill the baby... so the Divine one raised it as his own, teaching the child the good ways... but the child turned evil regardless. So the divine one finds out about nemises, and bans the child to nemises (this would be your death knight) and casts a spell so that the child cannot leave nemises through a normal rift. On nemises magic doesnt work the same way as in rivellon, so the DK cant use magic initially, and has to learn how to use their magic and rifts.
