Stress relief and piety from from torture and executions
Raid for prisoners without having to select a CB that pushes you towards overextension
Blood refills from vampire executions
No blood bond effect from feeding from your herd


It just seems too easy once you've got past the admittedly difficult step of getting established, you effectively get the ability to use prisoners as sorcery/blood sorcery/psychic batteries, spamming powers then just using torture + exsanguinate on a single prisoner to take your stress and hunger to 0. Keep your herd on torture rotation and you can run an umbra expedition every cooldown without worrying about stress