Sukracharya was a Bhargava rishi of the Atharvan branch and a descendant of sage Kavi. The Devi-Bhagavata Purana refers to his mother as Kavyamata.
Sukracharya went on to study the Vedas under the rishi Angirasa but he was disturbed by Angirasa's favouritism for his son Brihaspati. He then went to study under rishi Gautama.
2) Sanjivani mantra:
He later performed penance to Lord Shiva and obtained the Sanjivani mantra (a formula that revived the dead).
He married Priyavrata's daughter Urjaswathi and they had four sons — Chanda, Amarka, Tvastr, Dharaatra and a daughter by name Devayani.
3) Asura Guru:
During this period Brihaspati became the Guru (Preceptor) of the Devas. Due to the hatred he bore towards Vishnu for what he perceived as the murder of his mother as she had given shelter to some asura whom Vishnu was hunting, Shukracharya decided to become the Guru of Asuras. He helped them achieve victory over the Devas and used his knowledge to revive the dead and wounded among them.
In Puranas and Itihasas, we find that the "Devas" are the Godly beings and the "Asuras" the demonic ones. According to the Bhagavad Gita (16.6), all beings in the Universe partake either of the divine qualities (Daivi Sampad) or the demonic qualities (Asuri Sampad). The sixteenth chapter of the Bhagavad Gita describes the divine qualities briefly and the demonic qualities at length. In summary, the Gita (16.4) says that the Asuric qualities are pride, arrogance, conceit, anger, harshness, and ignorance.
The Padma Purana says that the devotees of Vishnu are endowed with the divine qualities (viṣṇu-bhaktaḥ smṛto daiva) whereas the Asuras are just the opposite ("asuras tad-viparyayah").
Rakshasas are notorious for disturbing sacrifices, desecrating graves, harassing priests, possessing human beings, and so on.
In the world of the Ramayana and Mahabharata, Rakshasas are a populous race of supernatural humanoids who tend toward evil.
Powerful warriors, they resort to the use of magic and illusion when unsuccessful with conventional weapons. As shape-changers, they can assume various physical forms, and it is not always clear whether they have a true or natural form. As illusionists, they are capable of creating appearances which are real to those who believe in them or who fail to dispel them.
Few exceptions were like Vibhishana in Ramayana and Ghatotkacha in Mahabharata who joined with noble.