Here is the shadeshine as held by the last Satab of Ventooine. The shadeshine was a unique type of stone. Upon making contact with it, a person's senses would be amplified to an extreme level. Certain senses, such as sight and touch, would transform into both transmitters and receivers. The individual who touched the stone gained the ability to accelerate the metabolism of others, manipulate the temperature and density of the surrounding space, and wield other powers. However, touching the stone came at a deadly cost: the person would perish within a year. Their senses would become so acutely attuned to external stimuli that their body and mind would be unable to cope. Ultimately, the person would suffer a painful death, essentially burning up from within.
The monarchs of Ventooine, known as the Satabs, possessed the only known shadeshine in the galaxy. Each year, the current Satab would select their successor, pass on the stone, and then enter a state of suspended animation. Han Solo brought an end to this tradition and the Satabs' rule. He accomplished this by killing the last of them and destroying the shadeshine. He did this by throwing it into the thrust tubes of the Millennium Falcon during a visit to Ventooine in his smuggling days.
The comic book provides an explanation of the Shadeshine's power, but it does not reveal the origin of that power. It remains unclear whether it is an object that is Force-sensitive or whether its properties are a natural effect of this particular mineral on Humans (and potentially other species), entirely unrelated to the Force.