Previously known as Vaporized Aetherium in Beta, now is renamed to Dimagnetium.
During Story Mode, it's dropped by the worm which will drop 0-5 of it. It is dropped mainly by demonic creatures that drop it in quantities of 5-10.
It has many uses. It's mainly an augment. It can be added into wood to make float-wood (wood lighter than air). It can also be added into a railgun.
It is also a fuel. Railguns augmented with Dimangetium, heaviside coils use it too.