Time Sentinel

s were responsible for maintaining the scribbled timelines on the Axis. They had rounded heads, and their skin had various colours, blue, red and white among them. They were able to display images and symbols on their heads, including several incarnations of the Doctor and his TARDIS. They were present on prehistoric Gallifrey, where they threw time sensitives into the Untempered Schism.

The Doctor stated that he had seen something like them a long time ago, and he furthermore initially believed that they were Matrix agents. (COMIC: Old Girl)