Basically, Goldrinn is an Ancient, a demigod animal of the Night Elves; he, along with other Ancients, fought against the invasion of the demonic Burning Legion.
Tho he was killed, since he's a demigod, he entered a spirit form and over time, he was able to regain his physical form.
He's the spirit of courage and ferocity, but also leadership.
Fitting, wouldn't you agree?