God created all things including Satan and his messengers. Col. 1:16, Rev. 4:11
Jesus was tempted by Satan. Matt. 4:1, Luke 4:2. Satan entered at least 2 disciples where we are told so by direct scriptural statements showing Satan having done this. The children of the devil (demons) were also in the pharisees that Jesus addressed in John 8:44. Jesus said that where the Word is sown, Satan enters the heart to commit sin. Mark 4:15. John the Apostle linked the devil to "sin" in 1 John 3:8, showing how extensive this problem is for everyone. Paul stated he had a messenger of Satan in his own flesh. 2 Cor. 12:7.
And yes, there are many direct references to Satan in the O.T. Most of them in Job. But also in 1 Chron. and Zech.
There are an abundance of 'allegorical' term references to Satan throughout the scriptures. Dragon, red Dragon, Pharaoh, behemoth, leviathan, thorn, thistle, serpent, crooked serpent, piercing serpent, belial, etc. etc. Really too extensive of a study to even get into in this format.
When believers understand the principle of Mark 4:15 they should read the scriptures accordingly. They'll learn to understand how God Speaks to people i.e. God is NOT addressing only people when He Speaks. God Speaks His Words, Satan resists His Words IN man. Therefore God speaks to TWO separate parties IN MAN when He Speaks. Acts 26:18, Romans 11:8, 2 Cor. 3:14, 2 Cor. 4:4, Eph. 2:2 and many many more.
But if believers take personal offense at this, they really heard nothing, and the scriptures will be partially blocked from their understandings. It is basically impossible for any believer to see this unless and until God in Christ leads them to see it in relation to their own sins and temptations.
If Jesus was tempted by Satan do we expect any different for ourselves? Uh, no. Temptation transpires "internally" and that places the tempter "in the flesh, internally" to do so.