You have found a way to harness the power of soul sand in order to trap the souls of mobs inside of eggs. The only material powerful enough to hold this enchantment is gold. A normal enchantment table does not have the capability to create this enchantment. A player must perform a ritual in order to enchant their golden sword with Soul Steal. You do this by dropping a golden sword on soul sand, while you have 30 levels. You then drop 3 lapis on different sides of the sword to enchant it with Soul Steal. After the sword is obtained, you simply have to kill mobs with the sword while eggs are in your inventory. The process is still not perfect however, the sword only has a small chance to capture the soul in an egg. Failed soul captures with destroy the egg, so make sure to stock up on eggs while hunting for souls!