1. More of the Istari
Emissaries they were from the Lords of the West, the Valar, who still took counsel for the governance of Middle-earth, and when the shadow of Sauron began first to stir again took this means of resisting him... - The Istari, Unfinished Tales
Background The Istari were a group of 5 wizards who were sent from Valinor to rise against the menace of Sauron should he come forth again. Of the 5 that were sent by the gods of Middle-earth- the Valar- only 3 are really mentioned in LOTR and inferred in The Hobbit: Gandalf the Grey (also known by his Elvish name Mithrandir), Saruman the White (Curinir in Elvish), and Radagast the Brown. The other 2 blue wizards, Alatar and Pallando, disappeared from the tales of Middle-earth. Tolkien speculated on what may have happened to them in his letters to friends, proposing that they may have formed cults for magic worship in the East of Middle earth, having been distracted from their true mission to contest the rise of Sauron. These wizards were in reality Maiar, angelic spirits of the same order as the Valar, but possessing far less power and influence. They clothed themselves in the forms of older Men, though they possessed greater innate strength of body and mind and aged slowly, if they aged at all. The Valar strictly forbade them to match Sauron's inevitable rise to power with displays of power of their own- rather they were to guide and influence the inhabitants of Middle-earth to action (though not by dominating them). As we see in LOTR when Saruman disobeyed this command he was stripped of his power and banished from the order. Members of the Istari came to Middle-earth around the year 1050 of the Third Age, when the forest that had historically been known as Greenwood the Great fell under the shadow of the Necromancer of Dol Goldur and became known as Mirkwood. Mirkwood features prominently in The Hobbit.
Film vs Book In The Hobbit book, Radgast the Brown is mentioned briefly in the chapter Queer Lodgings as the cousin of Gandalf (a term most likely meant to denote that they were of the same order). Gandalf used Radagasts name as a way to convey his good intentions, aware that Beorn knew of him as an honourable character- "not a bad fellow as wizards go". We know that Radagast will appear in the movies, portrayed by Scottish actor Sylvester McCoy. Radagast is likely moved to action by the darkness that he sees creeping over Mirkwood- as a lover of birds and the creatures of the forest, it may be him who first motivates Gandalf to assess the menace of Dol Goldur. Likewise, Saruman the White is set to appear in the movies, yet Saruman never appears nor is named in the book. His involvement in the events of The Hobbit can be inferred when Gandalf mentions in the presence of Bilbo the council of white wizards on their return to Rivendell- Sarumans actions during this period are principally revealed in the appendices to LOTR, first published in The Return of the King. Here we find out that fifty years before the events of Fellowship of the Ring- after his studies reveal that the One Ring might be found in the river Anduin near Sauron's stronghold at Dol Guldur- he helps the White Council drive out Sauron in order to assist in his own search for the One Ring. Which brings us on to