Mang is definitely not a horse. There's no common reference or understanding that Mang represents a horse. Maybe you heard it wrongly or it's a made-up term in a very specific context that's not widely known.
"Yes, I recommend the historical novel, Daxinzhu, to you. It tells the story of a person who traveled to the end of the Western Han Dynasty and became the son of Wang Mang. He helped Daxinzhu and brought peace to the world. The book also mentioned the author's new book, Prince Sui, which was also worth reading. I hope you like this fairy's recommendation. Muah ~😗
" Reborn into a Python: Dominating the World by Devouring " was a rebirth novel. It told the story of the protagonist Wang Mang, who became a giant python after his death. With the help of his family, he continued to evolve and grow bigger and bigger. The plot of the novel was fascinating and highly recommended.
The Northern Mang Female Empress was a character in Sword Snow Stride ". She was the Female Empress of the Northern Mang Kingdom and one of the most powerful people in the story. She had an emotional entanglement with Xu Xiao, but in the end, it didn't work out. The Northern Mang Female Empress chose to look for Xu Xiao after he died. She didn't want to continue living and didn't want to see Northern Liang fail. After she died, Beimang would destroy Beiliang and go south. The search results didn't provide any specific information about the Northern Mang Empress's ending or her relationship with Xu Xiao.
I've never come across the term 'mang bts'. It could potentially be a nickname or a code word within a particular group or community, but without more context, it's hard to say for sure.