"They are strategically killing me slowly in here. I have been humiliated over and over again," Black wrote beneath a photo of himself crouching with a smile on his face.
Black, whose legal name is Bill Kapri, described a "big conspiracy" going on in the facility and identified two prison officials — Lt. F. Arroyo and Santiago Torres — as those responsible for the alleged abuse.
"Lieutenant F. Arroyo has been very vindictive towards me and I have a strong feeling it has something to do with me being set up, laced, bruised and brutally beaten two weeks before my court date," Black elaborated. "There is a big conspiracy going on in this building on Me. Santiago Torres is using her position wrongfully in Miami FDC and is abusing her authority."
A spokesperson for the federal Bureau of Prisons declined to comment on Black's allegations.
According to Black, the officers wrongfully denied him phone privileges while he was in solitary confinement. The rapper also claims he was denied a visit from his mother two days before Christmas.
In addition, he suspects his incoming mail is being delayed and his outgoing mail is being tampered with. The rapper claims his family never received any of his holiday letters, which he finds "borderline cruel and unethical."
"But as if all this is not enough, on December 31 New Year's Eve to be exact, I was handed an empty tray for breakfast," Black wrote.
The Instagram post ends with somber words about overall conditions inside the prison.
"I am highly disappointed in the way they have treated not only me, but all the other inmates in this facility," he said. "With their self serving agenda they will always side with their fellow officers whether right or wrong."
Last year, law enforcement detained Black shortly before his scheduled performance at the hip-hop festival Rolling Loud at Hard Rock Stadium in Miami Gardens. He was accused of lying while purchasing a firearm from a Hialeah gun store; the weapon was later found in a shootout. The rapper, who already was facing sexual assault charges in South Carolina, provided a fake social security number on his background check form when he bought the guns.