Contact with Scarlet Night on bare skin will result in a swift and painful death. Victims of Scarlet Night are characterised by foam around their lips, blue faces, and blisters forming wherever the fungus made contact with the skin. However, if the fungus latches onto clothing, it will die in a couple of hours and become harmless to interact with. The dead fungus can then be used as a deterrent against various creatures, such as rats.
Secrets of Deltora
City of the Rats
In order to escape from the city of Noradz, Lief, Barda, and Jasmine had to pass through a tunnel covered in Scarlet Night. They stole the outfits of the city's leaders, the Ra-Kacharz, and were able to pass through the tunnel unharmed, while Reece—the leader of the Ra-Kacharz who they brought as a hostage—was killed just from coming into contact with the fungus.
In the anime, Scarlet Night is green coloured. When it comes into contact with bare skin, it seems to rapidly change the victim's body into a colony of fungus.