It is a soft, chalky material with a vibrant yellow coloration.

It maintains a constant ambient temperature of 645 C, resisting any attempts to cool or heat it. This internal heat means that, if kept in air, it is constantly surrounded by flame. Its most significant feature is that it is highly volatile. Almost any change in state will cause a mass of sulphurisse to explode with tremendous energy, usually destroying anything within about 100 times its radius and causing collateral damage in the form of toxic and caustic fumes. Sulphurisse is known to react to harsh impact, changes in its temperature of more than 3 degrees C, and exposure to numerous materials and compounds, including compounds of sodium and nitrogen. Because of its high instability, further research into its properties is almost impossible.

Sulphurisse is not naturally occurring, or at least natural formations of it do not last long enough to be found.

Sulphurisse is entirely stable as long as it does not explode; samples kept under extreme protection have been known to last for years without any change in condition or size. When it does explode, alchemists theorize that the microscopic debris return to their original sulfur form.

Sulphurisse was first discovered after Sulfur was isolated as an element. With retrospect, many historical mysterious explosions have been attributed to its presence.

Because of its high volatility, it is not in common use. Some alchemists experiment with very small samples, attempting to find any way of rendering it more stable, but have not yet found success.   Additionally, its existence has led to the banning of gunpowder in most countries. Errant wisps of raw magic are capable of transforming small amounts of sulfur into sulphurisse; if this new mass is combined in gunpowder, it will immediately react with the saltpeter that is also a component and cause the entire stock of gunpowder to explode. For this reason, it is widely accepted that gunpowder cannot be used or stored safely, and has been abandoned as a resource.