Halcytone was a type of paint that could be also used to control minds.
It was developed by Arnauld Klimt while he was creating his space slugs. Halcytone contained nano-optic particles which could change the colour and patterns in the paint. Thus it could be used to make changes without having to repaint. The particles could also relay information, allowing spying of painted areas. The patterns created could be used to hypnotise people. Aristotle Halcyon became blind whilst he was experimenting with it. (PROSE: To the Slaughter)