Just who is Odin?

[Mysteltain]

Steel Reign
Atop his mighty steed, clad in armor darker than the void, the elder primal Odin has returned to Eorzea to exact his brutal judgment upon the realm

I ask 'who' because while we know that he's an elder primal, there seems to be a bit more to him than the other primals we encounter in the story. Probably the biggest difference between him and the other primals is that he isn't--nor does he resemble--a beast of any sort. Before the FATE begins, Odin can be seen walking on Sleipnir without his helmet, and he appears to be a white-haired Elezen with a beard. Perhaps because he's an Elezen (or used to be?), that's why he appears in Gridania rather than anywhere else?

Also of note is that during the fight against him, he makes the statement that "Here I stand--a god amongst men. Yet here I remain--a mere man amongst gods." So did he somehow lose his 'primal-hood' or something?

The last part that I'm curious about with Odin is why does he want to find Urth so badly? When you fail the FATE, Odin will say, "Urth--one day, I will find thee." Who is Urth in the first place? I know that there are two places named after Urth in the Black Shroud--Urth's Fount and Urth's Gift--but who was Urth? Was his name mentioned at all in 1.0? I realize that I'm asking questions that there probably aren't any answers too, but I'm really curious about Odin in this game