Who Nirriti is
Nirriti is the goddess nobody wants to meet. Her name is an ordinary Vedic word that means dissolution: things falling apart, bodies wasting, luck running out. When the poets speak to that word as a person, she is Nirriti.
The Rigveda has no hymn in her praise. She appears about a dozen times, and almost every time someone is asking her to leave. One hymn, 10.59, sung over a man who is close to death, ends four verses in a row with the same wish.
Let Nirriti go away to places far from here.
Other verses say the same in other words. A prayer to Varuna asks him to drive her far off (1.24). A healer says he has brought his patient back out of her lap (10.161). A funeral verse asks the earth to keep the dead man out of her lap, as a mother would (10.18). When a dove flies into a house and settles by the hearth, the family takes it for her envoy and sings a hymn to turn the visit into a harmless one (10.165).
The Atharvaveda gives her a little more shape. She binds people. A charm for a sick man speaks of a collar that Nirriti has fastened on his neck, and of fetters made of iron, and it bows to her as it unties them (6.63). Another verse speaks of a black bird as her mouth.
The priests of the Brahmanas worked out where she lives and what belongs to her. Her colour is black. Her quarter is the south-west. Her share of the grain is the husk. Any spot where the ground has split open by itself, or where no plants will grow, is hers. The Shatapatha Brahmana goes further and says that Nirriti is this earth itself, in the mood in which it takes back whatever decays.
So she is worshipped, though in an unusual way. A king about to be crowned makes his very first offering to her, in a crack in the ground to the south, and walks away without looking back. The builders of the great fire altar carry three black bricks to the south-west for her and do the same. Each of these rites gives her what is hers so that she will leave everything else alone.