Owl scout



An owl scout can be summoned by the Priestess of the Moon and used to scout the map. Owls are invulnerable and can be controlled. Higher level owls last longer, can see further, and are faster. The owl can be incredibly important when used to camp over the enemy's army.

An elven ranger can summon an owl scout, an invisible green giant owl that cannot attack.

Speculation
It's speculated that Dori'thur is a Owl Scout, due to Dori'thur relation to Tyrande, a Priestess of the Moon, and its powers are related to Elune Power.