Celt

The Celts were a human ethnic group which inhabited Great Britain early in its history.

History
When the Romans drove the Celts out of England, they were allowed to settle in Avalon. (EDA: The Shadows of Avalon)

In a timeline which might have been invalidated by Big Bang Two, the Eleventh Doctor suggested in 102 that a Celt may have damaged the Cyberman guard near Stonehenge in Wiltshire. (DW: The Pandorica Opens)

Celt worship

 * Cessair was worshipped as the goddess Cailleach by the Celts, specifically the Druids. (DW: The Stones of Blood)
 * The Celts also thought of Saul as a local spirit. (NA: Timewyrm: Revelation)
 * The Celts considered the Bodach as evil spirits. The Celts possibly had a role in the construction of an obelisk and the Eye of Oblivion. (K9TV: Dream-Eaters)