Soul of Night

Soul of Night is a Hardmode crafting material dropped by all enemies killed in the Underground Corruption. This includes stray enemies not native to the biome, such as Goblins and Meteor Heads. Crafting all items, excluding the Boss-summoning items, requires 80 Souls of Night. One of each Boss-summoning item requires an additional 12 Souls of Night, for a total of 92.

Tips

 * An easy way to farm large numbers of Souls of Night is to summon the Eater of Worlds in the underground corruption area and quickly killing it with a Dao of Pow (normally drops 8-10 souls per kill, and a Dao can kill him in 30 seconds just being left on the ground). The same method, however, can not be used for Soul of Light, as Eater of Worlds would flee due to not being in the Corruption.