In the Bhagavad Gita, Sri Krishna reveals the qualities that define a divine or a demoniac nature. He talks about them in verse 12 and 13 of Chapter 9, and then elaborates on them in Chapter 16. He says in verses 1-3:
abhayam sattva-sanshuddhir jñaãna-yoga-vyavasthitih |
dãnam damash cha yajñash cha svãdhyãyas tapa ãrjavam ||
ahinsã satyam akrodhas tyãgah shãntir apaishunam |
dayã bhūteshv aloluptvam mãrdavam hrīr achāpalam ||
tejah kshamā dhritih shaucham adroho nāti-mānitā |
bhavanti sampadam daivim abhijātasya bhārata ||
O scion of Bharata, these are the saintly virtues of those endowed with a divine nature—fearlessness, purity of mind, steadfastness in spiritual knowledge, charity, control of the senses, sacrifice, study of the sacred books, austerity, and straightforwardness; non-violence, truthfulness, absence of anger, renunciation, peacefulness, restraint from fault-finding, compassion toward all living beings, absence of covetousness, gentleness, modesty, and lack of fickleness; vigour, forgiveness, fortitude, cleanliness, bearing enmity toward none, and absence of vanity.
The above qualities are called daivi sampat (divine virtues). In verse 4, he lists the qualities of a demoniac nature, called asuri sampat:
dambho darpo ’bhimānaśh cha krodhah pārushyam eva cha |
ajñānam chābhijātasya pārtha sampadam āsurīm ||
O Partha, the qualities of those who possess a demonic nature are hypocrisy, arrogance, conceit, anger, harshness, and ignorance.
Sri Krishna goes on to list other qualities in further verses, like pretension, cruelty, impurity, absence of religious discipline, absence of truthfulness, absence of faith in God, endless desire for sense pleasure, delusion, false values, worry, attachment, greed, egoism, and slander.
It is not that some humans are divine and show all divine qualities, while others are demonic. The two types of qualities exist inside every human being, but the proportion varies. The essential struggle of human existence is that our higher self pulls us upwards towards divinity, while our lower self pulls us downwards towards demonic nature. Every human being has three types of gunas (qualities)—Sattvoguna, Rajoguna and Tamoguna. The way these three combine determines our swabhava (nature). Those who develop sattvic qualities rise to the higher levels; those in whom rajasic qualities dominate, remain in the middle regions; and those who fall prey to tamasic qualities, descend to the lower levels.
Lust, anger and greed are the foundations from which the demonic qualities develop. They fester in the mind and make it a suitable ground for all other vices. Consequently, Shri Krishna labels them as gateways to hell. In our swabhava, divine and demonic qualities are in a constant struggle. When this struggle gets out of hand, it comes out from inside us and manifests itself in the outer world.