Ravens were among the more intelligent birds to be found in Middle-earth. Not as noble nor as wise as the Great Eagles. Ravens were nevertheless on the side of good — unlike all too many of their lesser Corvidae cousins. They were reputedly the messengers of the ValaNámo (Mandos) and were associated with Fate and Prescience. The Ravens of Erebor had befriended and counselled the Dwarves of the Line of Durin during the Third Age.
These noble birds lived a long time: Roäc of Erebor lived past 150 years of age. Brilliant and somewhat enchanted, most Ravens could speak the tongues of the Free Peoples (or at least of Men and Elves; the tongue of the Dwarves was too secret and that of the Ents too lengthy for ravens to learn).
Conjurers had long sought out the foreknowledge of Ravens.