Silas Wain

Silas Wain was a human employed by the Pantheon of Champion Beings to be their agent provocaterur. He created obstacles for the Doctor to test him and see if he was worthy to be the Pantheon's willing sacrifice.

He was returned to his home era and planet, and the Doctor intended to have enough space between them as to never see him again. However Silas immediately ordered one of his subordinates to make a complete background check on Martha. He commented on the fact that, rather than a matter of space, it would only be a matter of time until he would see the Doctor again. (IDW: Agent Provocateur)