#1 & #2: Who is he? Where did he come from? Satan was/is the highest created angel, with God from the beginning, along with the other angels (Ez. 28:13). Sometime before the creation of mankind, Satan convinced 1/3 of the angels to rebel against God, ultimately with God and the remaining angels winning (Rev. 12:3-9). After this occurs, we know that Satan takes the form of a serpent in the Garden of Eden and convinces Adam and Eve to eat from the Tree of Life (Gen. 3:3-5), thus starting "The Fall".
#3:Where is he going or what will happen to him? Satan will always be in rebellion to God. Near the end of the days, a false prophet and a beast will be given authority to rule for forty-two months (Rev. 13:1-5), who will convince "the kings of the earth" to fight against God (Rev. 19:19) in the "Battle of Armageddon". God and his angels will defeat them, and they will be "thrown into the lake of fire"; Satan will be chained for 1000 years, and Jesus Christ will rule the Earth for this time (Rev. 20:2-3). Satan will again be released for a short time, for one more attack against God, but "fire from Heaven will consume the rebels". Finally, at this point, Satan will be cast into the lake of fire, to be tormented day and night, forever and ever (Rev. 20:7-10).