Souls

Souls are Hardmode crafting materials dropped by enemies. Unlike other enemy drops, Souls are not affected by gravity, and thus remain floating in midair at the point where the enemy was killed. For large enemies and Bosses, this is usually the enemy's head, regardless of where the final strike occurred.

All enemies can drop Soul of Night or Soul of Light, depending only on the biome they are in when killed.

Trivia

 * All of the Soul of... names rhyme with each other (-ight).