Probably best known for their concept Sci-fi themed concept album Operation: Mindcrime, Queensryche's sci-fi, with a touch of fantasy, themed songs go back to their first EP.

Including the fantastically 80s music video, complete with Star Wars style scroll intro and cutting edge 80s graphics, for Queen of the Reich (which the band took its name from). Featuring a post-apocalyptic future with kind of a medieval look.

And another from that album: Prophecy

And they even had a Vampire themed song (Walk in the Shadows) on their Rage for Order album:

After that, it was mostly sci-fi themed, including this gem from Rage for Order, Screaming in Digital.

And of course, Operation: Mindcrime has an entire album based on a programmed assassin, who is activated when he hears the phrase "mind crime", which happens at the start of the title track.