Twelve

You may be looking for the twelfth incarnation of a Time Lord who suffered from regenerative dissonance or the number.

Service Robot Twelve was a machine used in Snowglobe 7 in 2099. It was part of the rubble scavenged from the accident in one of the tunnels. The Tenth Doctor repaired it, to the surprise of the engineers, and used it to help him find the exact location of the accident. Somehow, it gained human emotions that made it afraid and agitated as it neared the accident site. (PROSE: Snowglobe 7)