Calendar Man

The Calendar Man was a being who judged others and, if they had not lived their lives well and wisely, killed them and erased all memory of them.

The Eleventh Doctor knew about the Calendar Man from Time Lord fairy tales and encountered him on Ryklan, where he had killed thirty people including Alan Sigraff and Marcus Haddon. The Calendar Man wanted to judge the Doctor and promised that, if he was unable to convict him, he would restore the memories of all those on Ryklan. He made the Doctor confess, but Olivia Pamiec wrote her name in the Calendar Man's book.

Since he had to kill whoever's name was in the book but would die if he killed an innocent person, he chose to write his own name, kill himself and live on in myths. The Doctor put his book in the TARDIS library, but the Calendar Man's ticking could still be heard. (AUDIO: The Calendar Man)