Etherium is a special material generated when shards combine. It is a silvery black material that can take on almost any property. Hard metals for forging, supple metals for jewelry or arcana, and even fine metal thread. It can also be turned truly crystalline to resemble metallic colored glass or gemstones... even beads.
Etherium can be used in the creation of magical ink or substrates to give an additional effect to scrolls and potions. The exact effect varies based on the spell, and will be discovered through experimentation. It takes 25GP of Etherium per spell level.
Etherium can also be used as a substitute for other materials when making magical items. Wondrous items crafted with etherium can be made to fit slots they would not normally fit. Such as a bracer of natural armor rather than an amulet.
Etherium can potentially be used to augment or replace parts of the body. Giving magical abilities similar to wondrous items, offering fortification and other armor enchantments, or a multitude of other effect that can be discussed with the DM. I suggest looking up the planeswalker Tezzeret from MtG and the Shards of Alara block to get some idea of what can be done.
Etherium also has a crystaline form that grants it the ability to levitate a hundred pounds of matter per 50GP of Etherium.
I should add that making any item with etherium will require a relevant craft check. So making a cloak of protection with etherium will take a tailor. Making magical armor an armorer. Just in case anyone was wondering why I asked them to choose crafting skills.
