Ultranium/Tenebris Ore

Tenebris Ore is a pre-hardmode  that generates during world creation. It can be found on the surface and requires 65% pickaxe power or stronger to mine it. Alternatively, you can also kill to get a guaranteed drop. Tenebris Ore can be used to create, which is used to craft early and endgame equipment, when used in conjunction with at a Furnace.