Lanterns are protective enclosures for a light source - usually a candle - used to make it easier to carry and hang up, and more practical outdoors or in enclosed interiors such as passages and staircases where unguarded candles were more likely to be blown out by gusts of air - not just from wind but even opening a door. Shinobi could use a variety of Japanese lanterns, as well as torches and palm fires. They needed to learn how to avoid lights and illumination.