The passage that narrates the three temptations appears in the Synoptics, but is ignored in the fourth Gospel. Furthermore, in the fourth Gospel Jesus could not spend 40 days in the wilderness after being baptized as told in Mark 1:12-13 (which is the source of Matthew and Luke). So, if the testimony of the author of the fourth Gospel were true (read John 21:24), the story of the wilderness never happened. Most probably, it was invented by a christian comunity to teach about the battle between the evil and the good.
About Satan, Deutero Isaiah did not believe in him, because Isaiah said that YHWH was also the source of Evil:
I form the light, and create darkness: I make peace, and create evil: I the LORD do all these things. (Isaiah 45:7)
http://www.jw.org/en/publications/magazines/wp20141101/who-is-the-devil/