Stien

Stien was a duplicated agent working for the Daleks.

Stien encountered the Fifth Doctor and Tegan Jovanka after they landed in London in 1984 due to falling into a time corridor. Stien escaped from the Daleks as he could not take the Dalek conditioning. He next travelled with the Doctor through the time corridor to a prison ship the Daleks had boarded.

However, the conditioning re-emerged and he threatened the Doctor and took him as a prisoner. He began processing the Doctor for the same Dalek conditioning when he began having second thoughts. With the Doctor's assistance, Stien was able to regain control of his mind.

Stien assisted the Doctor when he went to kill Davros, guarding him against the troops of Gustave Lytton while the two talked. He retreated to a control room where he defended himself once again.

Once the Doctor had left the ship, Stien activated the self-destruct mechanism, killing himself and all the Daleks on aboard. (TV: Resurrection of the Daleks)