This portion of the semblance is something August keeps from people as much as possible, hence the spoiler tags. Read at your own risk, with the knowledge that most characters won't be aware of this true nature.
August's semblance is the ability to dominate people beneath him. When he uses his semblance, his aura literally tries to embed itself into the soul of the target. If he maintains this contact for a full minute and the target is in a sufficiently submissive position morally or spiritually, August can force a connection that binds the target to his will. When this connection forms, August can send telepathic communication to the victim, but the victim cannot respond in kind. This telepathic communication is not bound by distance. Whenever August gives a command, either spoken or telepathic, to the victim, the victim must follow the command or face consequences. The command can be literally anything, though August can choose whether to enforce the command (For example, August can ask for the salt at the dinner table from a victim without invoking his semblance). That means August can issue suicidal commands, or even physically impossible commands.
However, August's semblance does not restrict free will. Any individual under the effect of August's semblance can refuse August's orders, but it comes at a cost, and the cost is determined by what stage of submission August implemented the semblance under. Whenever the consequences for disobedience are about to be invoked, the target in question will feel a severe sense of dread as a warning. The earliest stage August can impose his true semblance on someone is Stage 3, and any individual under the effect of this semblance without the protection of aura will most likely die if they disobey.
Those with aura, however, will experience adverse effects as a result of disobedience. At Stage 3, a hefty chunk of aura is damaged as August's semblance literally rips into the soul, and if the individual has unlocked their semblance, they will lose the ability to use it for about 30 seconds. At Stage 4, a much larger chunk of aura is damaged, and semblances are locked from use for an hour. At the highest stage, Stage 5, disobedience is highly likely to result in death, unless the victim is particularly hardy. If they do survive, their semblance will be lost to them for the day.
On the bright side, punishment for disobedience can only occur once per day, and, unless August is watching, he won't know if someone has disobeyed his orders. While disobedience can result in a hefty handicap, it is still entirely possible to ignore August while under these effects. Furthermore, the connection only lasts for 30 days, unless August resets it.
There is one exception to a target's free will: they cannot willingly directly attack August or knowingly cause him harm while under the effects. There is no punishment for attempting, however they will be unable to follow through on any attempt, as if they were physically restrained by an invisible force.