Know the enemy

Some time between Genesis 1:1 and Genesis 1:2 an angel that is now called Satan chose to sin. But who was he? In Ezekiel we get a glimpse of who he was.
Eze 28:11-19 Again the word of the LORD came to me saying, (12) "Son of man, take up a lamentation over the king of Tyre and say to him, 'Thus says the Lord GOD, "You had the seal of perfection, Full of wisdom and perfect in beauty. (13) "You were in Eden, the garden of God; Every precious stone was your covering: The ruby, the topaz and the diamond; The beryl, the onyx and the jasper; The lapis lazuli, the turquoise and the emerald; And the gold, the workmanship of your settings and sockets, Was in you. On the day that you were created They were prepared. (14) "You were the anointed cherub who covers, And I placed you there. You were on the holy mountain of God; You walked in the midst of the stones of fire. (15) "You were blameless in your ways From the day you were created Until unrighteousness was found in you. (16) "By the abundance of your trade You were internally filled with violence, And you sinned; Therefore I have cast you as profane From the mountain of God. And I have destroyed you, O covering cherub, From the midst of the stones of fire. (17) "Your heart was lifted up because of your beauty; You corrupted your wisdom by reason of your splendor. I cast you to the ground; I put you before kings, That they may see you. (18) "By the multitude of your iniquities, In the unrighteousness of your trade You profaned your sanctuaries. Therefore I have brought fire from the midst of you; It has consumed you, And I have turned you to ashes on the earth In the eyes of all who see you. (19) “All who know you among the peoples Are appalled at you; You have become terrified And you will cease to be forever."'"
First off how do we know that this is speaking of Satan? We understand this because of the statements in Verses 12 and 13 "You had the seal of perfection, Full of wisdom and perfect in beauty. You were in Eden, the garden of God; Every precious stone was your covering”. When we consider the underlined text we can conclude that this was no man. Verse 13 also speaks of the “day you were created” not on the day you were born as we would expect if this was speaking of a man. Also in verse 15 we read that “unrighteousness was found in you”, not that you sinned. This is clearly speaking of the first ever sin. Also in verse 15 we see “You were the anointed cherub who covers”, the word covers can also be rendered shields implying that this being was a guardian of some kind. So the total picture that we get here is of a perfect sinless being that guards who fell from that sinless state.