The Mistress Adriana goes to prepare the slave ponygirl Thaina for a hard training. The Mistress Adriana will ride slave Thaina on a mattress that has the exact consistency of sand in the desert, meaning it is unstable and very tiring. The ponygirl will have to endure at least 15 minutes of riding, always following on the right, without stopping, without drinking water and without eating. She'll just obey, be guided by her hair like it's reins, and receiving a lot of slaps on her ass to be reminded of who's in charge.