Levium is the name for several alloys, most commonly an alloy of iron and bismuth, but the first recorded alloy to display its peculiar properties was of iron and gold.
On initial observation, it appeared to be an odd color for its composition, but then it was discovered that its density did not match its weight. It was then discovered that everything around it was acting heavier than it should, and after triple checking their equipment they concluded that they had found something fascinating.
Further experimentation revealed that the effect was not only in a gradient, but that anything brought into the area of the effect would speed up proportional to the intensity of the effect, and that any object exposed to the effect would equalize its proportional weight with the objects around it. Any object brought out of the effect would do the same, and the time taken to equalize was dependent on the intensity of the change.
The current theory to explain these properties relies on a theoretical construct, called delta particles by most, replacing the earlier, less common usage of the term.
The theory is that all matter produces these particles, and under normal circumstances magnetically attracts and reabsorbs them almost immediately, allowing said matter to react, form gravitational links, and move. The way delta particles radiate causes surrounding concentrations to equalize, and the faster they are absorbed, the faster they are produced. In the case of magnetic and diamagnetic materials mixed enough to be considered a psudeoalloy, however, delta particles are often lost, and eventually radiate outward until they reach the edge of the mixture, causing an expanding cloud of higher concentration delta particles and producing the effects observed.