Demonite Ore spawns in veins of 8 or less, and can be found at any level. Demonite Ore drops 1 to 3 demonite orbs. Orbs can be used to create demonite blocks, which can in turn be used to create the Demonite Furnace. Demonite orbs can also be used to create the demonite golem.
Demonite Golems are the only golems to be able to swim in lava. They also get hurt when making contact with water or rain. Demonite golems attack other golems (that are not their own kind) in addition to attacking mobs.