Humanity expanded to a space fairing species after discovering the exotic matter needed for Faster Than Light Travel by navigating what became known as the "Temporal Void".

While the passengers & ship captain could remain shielded during an FTL voyage, the navigators had to remain exposed as ships passed through the temporal void.

Exposure to the temporal void left navigators with odd and sometimes colorful mutations from the radiation. Discoloration of the skin, deformation, and in rare events, complete changes to their chemical make up.

However, that's not the only threat posed to the navigators.

Rare events dubbed "Temporal Storms" were known to transform Navigators into a hyper intelligent sentient plasma. While this would bestow new ability to perceive space & time, the navigators would effectively become trapped in their space suits.