Demonite Bar

Demonite Bars are used to create unholy weapons, or together with Shadow Scales to make nightmare tools or Shadow Armor. Demonite Bars are crafted from Demonite Ore, which is dropped by the Eye of Cthulhu, Eater of Worlds, and as of 1.0.5, can be mined, though it is very rare.

Demonite Bars have moderately high value, so selling excess bars for profit may be a good idea. Note that selling raw Demonite Ore will yield the same payoff.