What is the reality of the Black Banners mentioned in the hadiths, when will they emerge, what is their belief, and what will they do?

The hadith that mentions the black banners is authentic, narrated by Al-Tirmidhi, Ibn Majah, Ahmad, and Al-Hakim. It indicates that three sons of caliphs will fight over the treasure (the treasure of the Kaaba), then the black banners will appear from the East. This hadith is authentic in meaning without mentioning "for he is the Caliph of Allah, the Mahdi." These black banners are not the banners of Abu Muslim Al-Khurasani; rather, they are other banners that will come with the Mahdi.