Pulastya Rishi is the father of a community of rakshasas. Mahabharata (Adi Parva, chapter 67) describes the class of Pulastya. Ravana, the king of Lanka, was born in this family.
Vayu Purana (61.84) says that Pulastya was one of the seven great sages.
Brahmanda Purana (3.1.50) considers him in the race of rishis – Maricha, Bhargava, Angirasa, Pulastya, Paulahas and Vasishta.
Brahmanda Purana (7.162) mentions that Pulastya belonged to the rakshasa community.
According to an account in Brahmanda Purana (8.62), there are mainly four kinds of rakshasas and Pulastya is one of them. The other races of rakshasas are Naibhtas, Gastyas and Kaisikas. Each of them has been further divided into seven sub races.
According to Vayu Purana, the Pulastyas were born during the Svayambhuva Manvantara.
Brahmanda Purana says that Pulastya was born from the fire, which was blown into the eyes of Pulastya.
Brahmanda Purana (2.12.30) gives another meaning to Pulastya as the one whose fame spreads all over the world.
The name of Ravana, the antagonist in the Ramayana, is popular as Pulastya. Perhaps the patronym, suggests how, despite atma born of a sage, one can degenerate to become a demon because of wickedness brought by evil influence; in the case of Ravana, the influence was that of his own mother.
Bibliography
Ancient Indian Tradition and Mythology: Puranas in Translation (1970) – Motilal Banarsidass, New Delhi
Encyclopedia of Hinduism Volume IX page 306