Satan: Evil Personified or God's Test to the Faith
Prosecutor of Heaven
Tester of Faith of GOD
Accuser of Mankind
Lord of Hell
Not often thought of an Archangel, it's important to remember that Satan was an Archangel long before he was associated as the Ruler of Hell and Evil, and nemesis of Mankind.
Literally his name translates as "adversary" or "accuser"
At the end of the day, Satan's job is to tempt humanity from being loyal to God. He test to see who is really worthy of God's blessing and mercy.