Future Demoness is a 1.9 Insane Demon created by MaJackO. It is considered to be his hardest level.
The level's original song was: "The Quick and The Dead" by Rudebrat, but it was then removed from Newgrounds and MaJackO replaced it with Supernova. The level isn't synced well with the music because of that.
Gameplay
The level starts with a mini cube section that features moderately difficult jumps, fake lines and numerous jump rings. Next, the player enters a more difficult dual cube segment. Afterward, the player enters a difficult UFO segment consisting of numerous tight spaces and spikes everywhere. Next, it becomes extremely hard with dual wave due to fake spaces and extremely crucial timing. It becomes less harder (still very hard) with it being single. And then the player will transform into cube again, right before a difficult ship sequence. Then, the player hops between segments like that until the ball part with many, many traps and gravity changes that needs crucial timing. And then it turns into a very difficult wave segment consisting of tight spaces, high speed and traps. And then it turns into a very hard half speed ship sequence. Then it turns into a even harder wave segment with traps that are difficult to notice, tight spaces, high speed and constant gravity changes. And then it turns into a very difficult fast mini ship sequence that needs insane memorization skills in order to pass. Then the level will end with a wave with the word "Thx." However, it will turn into an easy cube again before the level ends. However, it is possible to skip the cube portal easily by staying at the ceiling, thus entering the secret way. Then, the level ends.
Walkthrough
Geometry Dash - Future demoness by MaJackO (Demon) Complete (Live)
Credits to Krazyman50. This video shows the full walkthrough of Future Demoness.