I've cleared Nocturna's story on hard mode in Necrodancer. I was skeptical at first about the whole electricity thing, like "that's really the gimmick for the DLC?" but it's actually a lot of fun. But really the standout DLC addition is the onyx weapon type. Love those.
Frankensteinway (lol) as a boss is like, weird. If you go in without bombs to destroy the electric pylons I feel like it's impossible, but simply blowing up the pylons makes the boss almost too easy?
The Conductor (lol, but less derisively) is a great boss though. It's a really fun encounter and plays with the electricity in fun ways.