This yantra represents the Hindu god Narasimha, whose name means “manlion.” Narasimha is said to be the fourth incarnation of Lord Vishnu. Vishnu's Narasimha incarnation is in the form of half-man, half-lion in order to rid the world of the demon Hiranyakashipu.
Hiranyakashipu received a boon from Brahma, and requested immortality, but Brahma told him it was not possible. Brahma then said that he could bind the death of Hiranyakashipu with conditions, and Hiranyakashipu accepted this boon. The conditions were:
"Narasimha could not be killed inside or outside a building, by human being or animal, on land or in water, during the day or at night, death could not be brought about by any weapon, by any god, demi-god or demon."
In order to kill Hiranyakashipu and not negate the boon granted by Brahma, Narasimha is part-human, part-animal, he comes upon Hiranyakashipu at twilight (neither day nor night) on the threshold of a courtyard (neither indoors nor out), and puts the demon on his thighs (neither earth nor water). Using his sharp fingernails (neither animate nor inanimate) as his weapons, he disembowels and kills the demon.
The Narasimha Rakshana Yantra represents powerful protection from disturbing influences of all sorts. Rakshana means “protection.”
"O Keshava! O Lord of the universe! O Lord Hari, who has assumed the form of half-man, half-lion! All glories to You! Just as one can easily crush a wasp between one's fingernails, so in the same way the body of the wasplike demon Hiranyakasipu has been ripped apart by the wonderful pointed nails on your beautiful lotus hands." (from the Dasavatara-stotra composed by Jayadeva)