Using this spell it is possible to enhance the duration of another spell using sacrifice. The other spell is cast first, then a willing sacrifice is led to a specially prepared spot and slain. The energy of their death flows into the spell and lengthens it's duration significantly, turning a spell that lasts hours into one that lasts days, days to weeks, weeks to months, months to years, and years to Long Years. Death blessing can only be cast to enhance a spell with a duration of at least 1 hour, and only one that targets a place and not a person.
Alternatively the Black Mage may use this spell to ignore one burden incurred by casting some other spell. The burden is instead attached to the spirit of the sacrifice, which is held as a Tornrait or Ghost until the burden is released.