Maxwell's Light is a special Structure that appears in Chapters 5 and 6 of Adventure Mode. It will light up when approached, and will turn off when the player walks away from it.
Maxwell's Light cannot be destroyed and does not drain sanity when standing next to it. It's possible to light a Maxwell's Light with a Torch or Fire Staff. Standing among the eyes in the shadows around Maxwell's Lights will not cause them to disappear.
If the player sleeps near a Maxwell's Light, it will not light up upon waking up until they move out of the Light's radius. This also applies when Woodie awakens from Werebeaver form or when resurrecting via Touch Stone.