Druids gain these title by challenging the current holder of the title for the terrain, kingdom, or continent. These challenges are almost always non-violent and involve a contest of skills (hunting, knowledge, animals, botany). If the challenger wins they gain the title.
ArchDruid: A druid in charge of a specific terrain. There may be only 1 ArchDruid per terrain in a country and the terrain must exist on the continent naturally.
Great Druid: There may be one Great Druid per country on a continent. ArchDruids in that country answer to them.
Grand Druid: There is only a one Grand Druid per Continent. The Great Druids on the continent answer to them.
Heirophant Druid: There is only one Heirophant Druid in the whole world. All of the Grand Druids answer to them.