Death of the Endless by extension is below The Great Evil Beast, which is seen as the darker aspect of the Presence.
Death of the Endless like other conceptual entities is that if her concept is destroyed or removed from existence such as the concept of death is erased, she ceases to exist in existence as well.
Death of the Endless is abided by Ancient Rules, like the rest of the Endless (her siblings), as she is bounded to a complex set of rules and limitations. One which requires her not to spill the blood of her own family which is the endless. She cannot and must not fall in love with a mortal or the mortal's downfall is assured.