Datak Tarr is a fictional male Castithan in the Defiance television series who was portrayed on screen by Tony Curran. Datak is a shrewd businessman whose only in it for himself. When his son Alak Tarr announces that he plans to marry Christie McCawley, Datak sees his opportunity according to Castithan culture on getting his hands on the mine owned by Rafe McCawley. At the end of the first series, he has become mayor of Defiance and seeks a join the Earth Alliance which the previous mayor Amanda Rosewater had fought to oppose.
Although Datak obides by the customs and laws of Defiance, Datak still holds dear to some Castithan traditions. In the opening episode where the city comes under attack, a fellow Castithan does a runner when he gets scared. Datak demands he be punished according to the Castithan traditions.
In the next episode, the coward is captured by Datak Tarr and is tortured in the city square. The ceremony is interrupted by Irisa who frees the coward. Datak takes great exception to this but he backs off when Jeb Nolan appears. Later however when no-one is around, Datak knifes the coward to death.
When Datak is imprisoned at the beginning of the second series, he gets Dr Mew Yewll to perform a sexual act on him which has definitely taken the series in a different direction.
At the end of the first series, Datak is arrested for murder and put in a makeshift prison. He is not the only one whose there from Defiance, Doc Yewll is there at the same time. Much to her annoyance, he uses her to pleasure him.
He manages to gain his freedom in the second series and returns home. Whilst he is in prison, his wife Stahma has been running the business. Stahma demands that she has a say in running the business which he rejects and is forced to move out. Datak tries to win over his employees but fails to do so as they are now loyal to Stahma.
At the beginning of the third series, the Tarrs have left Defiance and have fallen in with Rahm Tak, a Castithan leaders of the Voltanis Collective. Rahm Tak wants to take control of Defiance and force the humans out. Rahm uses Datak and Stahma to sabotage various parts of Defiance security so that he can walk in and take over.
One of the things that the Tarr have to do is to destroy the arch over Defiance which they carry out. Other things they do is to sabotage weapons that would have been used to defend the city from any invasion.
Datak's betrayal is discovered and he is sentanced to death. Instead of being hung, he wishes to be put on a Castithan shaming rack which Amanda agrees to. When Defiance needs a way of disabling the Voltanis Collective, they turn to Datak and get him to carry the bomb into the enemys base. Datak agrees and when Datak tries to persuade Rahm of his allegiance, Datak cuts off his arm as a show of allegiance. The arm contains a bomb which when it goes off wipes out the Voltans base.