4) Istari (Maiar bound to mortal form, thus they are reduced in Power while in Endor as an Istari)
The Istari ARE Maiar, but they've accepted the adoption of mortal form (until their task is done), and the restriction on expressions of Power. It's certainly POSSIBLE that an Istari could expression some degree of power as a Maia, but that would go against their directive, so they don't, or they use a LOT of descretion.
When Gandalf confronted Bilbo regarding the Ring after the Birthday Party, Gandalf also 'pulled back his mantle', revealing a bit of the Maia majesty that is merely cloaked by his Mortal Form. But that's as far as the Istari should ever go, unless, well, unless they're staring down the throat of a Balrog or something, which doesn't leave them much choice with regards to refraining from exuberant expressions of Power. ;-)
Okay so I am not %100 clear on the dif between an Istari and a Maiar (say like Balrog).
The Encylopedia of Arda says...
"Istari - The order of Wizards, the Maiar who came to Middle-earth after the first millennium of the Third Age. Of these, five came to the northwestern regions; Saruman, Gandalf, Radagast, Alatar and Pallando. "
"Maiar - Of the many spirits that descended into Arda at its beginning, those of lesser stature than the Valar, though they were still powerful, were known as Maiar. Each of the Maiar was attached to the 'people' of a particular Vala. So, for example, the Maia Ossė, as a spirit of the sea, belonged to the people of Ulmo, while Curumo, the Maia who came to Middle-earth as Saruman, belonged to the people of Aulė the Smith.
In the Third Age, there were still Maiar in physical form to be found in Middle-earth. The most important of these were Saruman, Sauron (originally also of Aulė's people), and Olórin, known as Gandalf, who belonged to the people of Manwė and Varda."
The Istari are a sub-set of Maia. They were tasked for a particular purpose: to counsel and inspire the Free Peoples of Middle Earth to resist Sauron. They were forbidden to match power with Sauron directly, and instructed not to use their might and power to bend any to their will.
"Normal" Maiar are not bound to a physical form. The Istart were bound to the 'mortal coil', until their task was done (and Sauron defeated). Nearly all "Normal" Maiar ceased to openly roam Middle Earth before the First Age.
The Istari, the Enemies (Sauron, the Balrogs, maybe Shelob, by inheritance from Ungoliant, could be counted), and (possibly) others like Tom Bombadil and the Great Eagles were different from "Normal" Maiar, because:
A) They resided in Middle Earth after the First Age
B) They were bound to their forms, the Enemies by the way they used their Will to increase their power over the world, the Istari because of their mission, and the others .. who knows, some may even have been able release their Fana (mortal form) at will.
Originally posted by ben hur Hey, why don't we get in touch some time, I've got an old palantir sitting in my basement, we could have a little chat about the game?
ME TOO!
It's right next to my Interocitor...
[starts rummaging]
let's see.... Green Lantern Corps ring... Carmamilk secret... Map tp king Solomon's Mines.... Tic-Tac with some lint on it... AH!