The former Druid, Amergan, is a very unusual teacher; he is a spirit who met Colin MacLeod when he had just revived from his death. Amergan knew a lot about Immortals, and told Colin about his Immortality and The Game. Colin didn't really care, and only wanted to avenge himself on Marcus Octavius. Amergan followed Colin, and tried to make him stop and think rather than continue on a path of mindless vengence.
He can possess small animals, and insects, and constantly talks to Colin, who refuses to listen most of the time.