The Tairnadal have great respect for the natural world, though they don't share the same level of veneration of the Druidic Traditions of the Eldeen Reaches. Many of the ancestors of the Tairnadal were rangers or druids, who brought the power of nature to bear against the giants of Xen'drik. These druids countered the magic of the giants, retaliating with storms and beasts, and many of them took on animal shapes and carried their comrades into battle.
The Siyal Marrain ("horse watchers" in Common) are the druids of the Tairnadal. They don't have the same veneration of the natural world that is found amongst the Druidic Traditions of the Eldeen Reaches, and largely view nature as a tool and as a weapon. The Siyal Marrain venerate their ancestors, like all of the Tairnadal, and their patron ancestors are legendary druids. As such, the traditions of the Siyal Marrain actually predate the druidic traditions that branched off of the Gatekeepers traditions by several thousand years.
The Siyal Marrain care for the legendary horses of the Tairnadal. The Tairnadal's own legends claim that these steeds (and the other Tairnadal animals) were ancient druids that were trapped in their animal forms by a curse cast by the Sul'at League in one of the most fearsome battles of the Elven Uprising, and that this is the source of the special abilities these animals possess. The Tairnadal believe that their animals, most of which are horses, are descended from these druids and that these ancient druids' spirits live on in their descendents, and as such they are to be afforded the respect of any of the Tairnadal ancestors. For the Tairnadal, a horse is not simply a tool to get from one place to another, they are siblings.
The Siyal Marrain are also tasked with caring for the land itself, and the druids in Valenar have had a drastic impact on the quality of the soil and plant-life since the secession of Valenar from Cyre. Siyal Marrain druids ride with all of the Valenar warbands and ensure that they don't overconsume the lands resources, encouraging them to live sustainably with their environment.