Collaborator Druids
While we've portrayed all the Celtic peoples with Druids in them as a single entity for the purposes of this list, they were quite capable of being cruelly toward one another. For instance, Druids of the Trinovantes people, who lived where Essex and Suffolk are today, provided significant assistance to Caesar's soldiers during their invasion of Gaul. Their main type of assistance was giving the Romans geographic data, which was crucial for an ancient army in a strange land.
As it turned out, the Trinovantes had a legitimate motive for supporting the Romans over their own race: members of their red-headed tribe were frequently chosen to participate in the sacrifices as "volunteers." Caesar gave the Druids what they desired when he ordered a halt to human sacrifices, despite the fact that he never personally interacted with any of the Druids. Alternatively, as we shall see, he provided them with their immediate desires.