A great king for whom the Dwarves of Erebor had made spears, which were never delivered or paid for.
See also: FAQ/Who was King Bladorthin
King Bladorthin and his history is nowhere else mentioned in Tolkien's writings, but Humphrey Carpenter, in his TolkienBiography, mentions that in the manuscript of The Hobbit, Bladorthin was the name of the wizard, whereas Gandalf was the name of the chief dwarf.
Robert Foster, in his guide  mentions that Bladorthin was "probably an Elf", whereas Douglas Anderson, in his "Annotated Hobbit" , suggests that he "may have been a man rather than an elf".
However, the name Bladorthin seems to be of Elvish origin. The first part blador, elsewhere found in Bladorwen, another name for Yavanna which is glossed as "the wide earth", "Mother Earth" (in Tolkien's GnomishLexicon? related words are blant 'flat, open, expansive, candid', blath 'floor', bladwen 'a plain'). The second part, -thin represents the Sindarin element 'grey'. Christopher Gilson suggests (in a letter to Vinyar Tengwar 17:1) that blador could also be an agent noun of the meaning 'wanderer, ranger, pilgrim'. Hence Bladorthin could (like Mithrandir) be rendered to "grey pilgrim".