Nephthys was an Egyptian goddess associated with birth and death, just as this monster keeps being reborn when it is killed. In Egyptian mythology, Nephthys was in fact the mother of Anubis, therefore making her the true Queen of the Underworld.
The idea of this card reviving itself from the Graveyard comes from the idea of a Phoenix being able to revive itself.
This concept is also exemplified in "Fire King High Avatar Garunix", a monster that also partly takes after a phoenix and whose first effect is very similar to this card's.
Additionally, both this monster and "Horus the Black Flame Dragon LV8" have the same blue gem seen on the Egyptian God Cards, and their names are bases on Egyptian mythology, like the Egyptian God Cards as well.
"Horus" and this monster also both have "Metaphys" counterparts.