Blood spell

A blood spell was a spell used by Kali to bind other beings to her.

Use
According to Gabriel, the blood spell prevents the escape of beings bound to the caster, effectively preventing the Archangel to apport Sam and Dean out of the Elysian Fields Hotel. The bind could only be broken once the caster herself lifts the spell, or if the blood used for the spell was taken away from the caster.

Procedure
The spell required only the blood of the target, regardless of the manner of acquisition. The spell was not dependent on the amount of blood. As long as blood of any amount was acquired by the caster, the spell would take effect. Beings who use vessels are not immune to the spell, as demonstrated when the archangel Gabriel himself was bound.