An issue with the Steppe Horde
I know that Scythia can turn into a Steppe horde at the end of their mission tree. However, I sometimes see the tribes north of Bactria becoming a horde as well, so I wanted to play as one of the tribes with the Alani culture, turn into a horde, and sweep down toward Bactria and the Seleucids.
The problem is, when I tried playing them, the option or mechanic to become a horde never appeared... Can someone explain to me why this is? I want to know if this is something only the AI can do.