If we go by the idea that the whole album is a concept album (which the video for Queen of the Reich hints to), then this song tells about some sort of troop of shock - while there are few lyrics and one can wonder if they serve a purpose in the story of such a short album (where every second is important), there are a few underlying themes to find out:
this song reinforces the mood of this Reich. The Nightrider (which is possibly a collective name for a whole army) instills fear and uncertainty.
He is afraid of nothing, and will stop at nothing to accomplish his goal - which he is always eager to take on, it seems (The Nightrider sails away, indicating a long voyage). People have reason to dread him; they are powerless against him.
Finally, his work is always done perfectly (By day the rider will have vanished from their eyes...). Resisting against him only delays the inevitable.
We could link this song to Queen of the Reich - in the beginning of that track, it is said that the Queen can come and take you away in the dead of the night... what if it wasn't the Queen doing the job, but the Nightrider?
-> However, the song is very vague on this. Judging from this vagueness, it is entirely possible that the Nightrider does not work for the Queen but for himself - he is friend and foe at the same time.
If we go by the idea that the whole album is a concept album (which the video for Queen of the Reich hints to), then this song tells about some sort of troop of shock - while there are few lyrics and one can wonder if they serve a purpose in the story of such a short album (where every second is important), there are a few underlying themes to find out:
We could link this song to Queen of the Reich - in the beginning of that track, it is said that the Queen can come and take you away in the dead of the night... what if it wasn't the Queen doing the job, but the Nightrider? -> However, the song is very vague on this. Judging from this vagueness, it is entirely possible that the Nightrider does not work for the Queen but for himself - he is friend and foe at the same time.
And remember... beware of the night.