Just by flipping the floppy disk, we've been magically transported from the pirate coast back to generic sword & sorcery waters. Back to right where the very first part of the series left off: that story's bad guy has kidnapped the familiar princess and keeps her prisoner on his castle. The king can't just send his army, as that would cause a major diplomatic crisis with the already not too friendly neighbour. So our adventurer has to take things into his own hands again.
Part 4 balances this very generic plot out with some quality gameplay contents. Game length has been increased and once entering the castle, it even becomes somewhat non-linear. Which prior parts had also pretended to be, but eventually, it all boiled down to exhausting all options until hitting the one which progressed the plot. This castle, on the other hand, actually allows for different paths and strategies: will you barge in, sword drawn, as usual, or will you try to trick the inhabitants? Each method providing slightly different information. It further helps that the game features a good number of characters. Probably, motivation will even remain sufficiently high to give it a second run after finishing.
The plot originating from an already trodden earlier episode is both boon and bane. In theory, it's not a bad idea to try and build a certain continuity between episodes, but then, the game doesn't reflect this in its gameplay at all. Regardless of whether the player reactivates a veteran character or generates a new one, the game will spit out identical texts, which tell of already finished adventures or have the baddie mention that he immediately recognized the hero, for example. Which couldn't possibly the case if the player character is a new one. The way it is, it transports the feeling of cheap product placement ("Buy these other series installments!").
Regardless, Die Burg des Magiers is the series highlight so far (not just due to a certain blonde singer making a guest appearance)! It being bundled on the same disk as the rather weak Piratenhaus was probably not quite accidental: buying this disk would have still been worth it overall, even if one of the adventures hadn't been that satisfying.