Well, by the third evolved form Rakban is really coming to life. He nearly carries on conversations with you

It's only cool, not good, but it's REALLY cool. He celebrates your victories with you, comiserates over defeats. Laughs at your friends who die. Praises your abilities in battle. Helps (spiritually) with discovering and scouting new areas. He is feral, so sometimes he gets a little worked up when entering a hunt, or taking down prey.
He's the best cheerleader you'll ever have in EQ. Even though he's a complete barn, I love having him around. It's the closest I've gotten to that "never alone in the world" feeling that I always had with my magician, and I really appreciate it. Doggie is nice, and the Spirits that are Called, but there's no question that you the shaman is the leader of that pack. It can be lonely at the top, but Rakban is up there with you. He's a pack leader, too.
The fully evolved mask is by far my favorite posession in game, past Vermillion Sky Ring, Braided Horsehair Handbag, and Skull of Vishimtar.