Here is what traditionally is said of druids:
The druid is a versatile supportive class, capable of casting divine spells, and also in combat. They gain divine magic from being at one with nature, or from one of several gods of the wild. They not have special powers against undead and cannot use metal armor. Wisdom is crucial to druids, as it determines their access to divine magic and aids many of their wilderness skills. Druids have the unique ability to shapeshift into various animal forms as well as summon them. How well their access to the natural forces and therefore their magic is while in a dungeon is not clear, druids prefer to be outdoors.
As the game goes on, we will find out more about Celtor and his skills.