Celt

The Celts were an human ethnic group which inhabited England 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 negated timeline 102 A.D., the Doctor suggested that a Celt may have damaged a 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)