Sibyl

The Sibyl started a soothsaying cult, the Sibylline Sisterhood, in Pompeii. She lay down the Sibylline Oracles.

It is unknown why the Sibyl started the cult or what she used it for, but the Tenth Doctor stated that she ran the cult less violently than when they tried conquering Earth with the Pyroviles in 79. The Doctor was said to have had a brief relationship with Sibyl, but the Doctor thought that it wouldn't work, to which she replied "I know." (DW: The Fires of Pompeii)