The Eldeen Reaches are the birthplace of Khorvaire’s druidic traditions. Indeed, this wild land supports many druids of dozens of differing sects. But the druidic traditions of harmony with nature and, especially in Eberron, defense against corruption are not confined to the Reaches. Any culture that is close to nature or to land with extensive undeveloped regions is likely to support druidic traditions.
Druids exist all across Khorvaire, and the other continents have their share as well (though less is known about them). In addition to the wild defenders most people think of, there also exist druid sects dedicated to the destructive aspects of nature. Although their followers are grim and dangerous, such traditions are not usually evil. Other druids do follow a dark path, incomprehensible to most, that honors ancient horrors or alien environments, seeking to change the very face of Eberron.
Many druids do not distinguish between the Material Plane and any other. Far from being “alien” and “outside,” to them all the planes are natural parts of the whole of existence. Other druids, generally those of extraplanar origin, are dedicated to the primacy of their home planes over all others. Agents of these outsider sects are drawn to manifest zones on Eberron, where they try to strengthen the planar connection, or even try to create new manifest zones.