Across the Complex, there is a market for soul eggs. They are expensive to buy and rare to find, but for phoenix there is unlimited money to be.
Some phoenix have discovered how to purge the soul from the egg while keep the function of the egg intact. They take them from mortuaries mostly, either stealing or getting them cheap from the unsuspecting assistants. Some phoenix have even found out how to take the egg from a living phoenix, including themselves, and letting a new one grow.
Once sold, the eggs are surgically implanted into whoever wanted it. They're soul seeps into these eggs, which allows them to live on like the phoenix do. However, they never remember their former lives and most times the young have issues with development.