Ruther
From Tardis Wiki, the free Doctor Who reference
Ruther was a citizen of Castrovalva. Like all residents of the city, he wasn't real, but rather a Block Transfer Computation created by the Master. He and his hunting party discovered the Zero Cabinet and the Doctor, and took them to the city. Later, he tried to attack the Master, who made Ruther vanish. (DW: Castrovalva)