The Zanti sent this ship to Earth specifically because they are as a species incapable of executing their own and they know humans are "practiced executioners".
The prisoners were watched over by guards of the same violent persuasion as the prisoners themselves.
It's full capabilities are unknown but they are sufficient to cross from planet Zanti to Earth.
It is shown to move in three dimension while in Earth's atmosphere.
It held inside an excess of one hundred Zanti.