Unlike souls obtained from the other mechanical bosses, the Souls of Might are relatively easy to collect as they don’t fall far away or high in the air, but instead fall from the body segment of The Destroyer closest to the player, often so close to the player that they can be picked up immediately. Souls of light are in underground holiness, while souls of the night can be found in underground purple or corruption. Souls of light are found in underground holiness, while souls of the night are found in underground purple or corruption. You can also call Eater of Worlds Boos (or its analogue in purple), and from each of its segments, one soul will drop out with a probability of 1 to 7.
This includes enemies that are not native to the biome, such as granite elementals.