I wish to know everything that the scriptures say about Kali demon of Kaliyuga.
Here, is description of Kali demon from Kalki Purana;
After the annihilation, the secondary creator of the universe, Lord Brahma, the grandfather of everyone, who was born on the universal lotus flower, created Sin personified, having a black complexion, from his back. The name of Sin personified was Adharma By faithfully hearing about, chanting, and remembering the descendents of Adharma, one quickly becomes freed from all sinful reactions. The wife of Adharma, (Irrehgion), was named Mithya, (Falsehood) She was very beautiful, and had eyes like those of a cat They had a son named Dambha, (Pride), who was always very angry and eneigetic. Dambha had a sister named Maya, and within her womb, he begot a son named Lobha, (Greed), and a daughter named Nikrti, (Cunning) Lobha begot a son named Krodha, (Anger), in the womb of Nikrti. Himsa, (Envy), was Krodha's sister. From the womb of Himsa, Krodha begot a son named Kali. Kali is always seen to be holding his genitals in his left hand. His complexion is very black, like black ointment that has been mixed with oil. Kali's abdomen is like that of a crow, his face is frightening to behold, and his tongue is red and appears to be full of greed. His appearance is very fearful and a bad smell emanates from his body. Kali is very fond of playing chess, drinking wine, enjoying the company of prostitutes, and associating with gold merchants. Kali's sister was Durukti, (Harsh Speech). From Durukti's womb, Kali begot a son named Bhaya, (Fear), and a daughter named, Mrtyu (Death). Bhaya begot a son named Niraya (Hell) from the womb of Mrtyu and Niraya begot ten thousand sons in the womb of his sister, Yatana (Excessive Pain). Thus I have described the destructive progeny of Kali, who were all blasphemers of genuine religious principles. All these relatives of Kali were the destroyers of sacrifice, study of the Vedas, and charity, because they transgressed all the Vedic principles of religion. They were reservoirs of mental distress, disease, old age, destruction of religious principles, sorrow, lamentation, and fear. [Kalki Purana 1.14-22]
HOLY SCRIPTURES SAYS ABOUT KALKI MAHA AVATAR
It is prophesied that Lord Kalki will appear at the conjunction of the two yugas, namely at the end of Kali-yuga and the beginning of Satya-yuga. Thereafter, at the conjunction of the two yugas, the Lord of creation will take His birth as the Kalki incarnation and become the son of Visnu Yasa. At this time the rulers of the earth will have degenerated into plunderers. "(Shrimad bhagawatam Maha Puran 1;3:25)"
Maharshi Ved Vyasa ji Prophesied in Shrimad Bhagawatam Maha Puran - "Lord Kalki, the Lord of the universe, riding His swift horse Devadatta and, sword in hand, will travel over the earth exhibiting His eight mystic powers and eight special qualities of Godhead. Displaying His unequalled effulgence and riding with great speed, He will kill by the millions those thieves and rogues who have dared dress as kings.