Blackbloom is a plant from which the world derives its common name. Its origins are somewhat in question, but its effect is undeniable.
If a blackbloom is placed in the mouth of the deceased, they rise in three days, undead but free-willed.
Blackbloom is rare, grows on no other planet (despite people trying), and is expensive. Some cannot afford it and so pledge a time of their unlife to indentured servitude in return for the bloom.
Blackbloom marks its users with a fine dark lattice just under the skin where the blood is stained. It is particularly notable on the face, genitals and upper chest where flushing is apparent.
Those who have consumed the blackbloom cannot leave the planet, and will use the "Unbloomed" (those who have not yet died the first time) as aids in off-planet business.