Many try to dismiss the fact that the Bible declares that there is a very real spiritual being called Satan. Various names are given to Satan, including: the “Devil,” (Greek diabolos), “serpent/snake,” “Abaddon,” “Beelzebub,” and “Belial.” His name means “adversary” and “deceiver.” He is also described as “a liar and the father of lies,” “a murderer from the beginning,” and that “there is no truth in him” (John 8:44). He is your “accuser” before God (Revelation 12:1, Job 1), “the prince of the power of the air [this fallen world]” (Ephesians 2:1-2), the “the god of this age” (2 Corinthians 4:4), and “the ruler of this world” (John 12:31). Note, however, that he is not called “Lucifer” (see the Lucifer as the Devil false teaching).
Many claim that the devil is just an idea, a concept, a myth, or a fairy tale. But here’s an analogy to help you understand this point: we don’t have to know where the Law of Gravity came from, or even need to understand it fully, in order to know that it is very real indeed and that there are dire consequences for ignoring it. The same goes for Satan.
It is interesting to note that in the documented exchange between Satan and Eve in the Garden of Eden (Genesis 3:1-19), Satan uses his tried-and-true tactic (which he still uses today) of deliberately twisting God’s Word with the intent to deceive and to spiritually/eternally kill all of the human race which was being born. Satan does this by either adding to, subtly altering, or taking away from God’s Word. This is why a Christian is strongly admonished to know the Word of God for themselves, so they are not deceived.
The Bible doesn’t tell us exactly when Satan was created, but it does say that he is a very real created spiritual being, an angel. As a created being, he is therefore not omniscient (all-knowing), omnipresent (able to be everywhere at once), or impotent (all-powerful) like God is. And Scripture tells us that he “prowls around like a roaring lion, seeking someone to devour” (1 Peter 5:8). So yes, Satan exists, and he means to destroy you – to kill you eternally. He tries to do this by obfuscating the truth of Scripture, by telling lies, half-truths and distorting (misquoting) Scripture. He is the “father of lies.” Below is an excerpt from Beyond the Tomb: 
Satan opposes everything good and of God. His main weapon today is deception. The false teachings in this section of the book are of his doing, as he attempts to deceive people out of believing in God, in the Bible, in Christ, and then even after they are born again, to try to cause them to stumble and “fall away” from the faith, backslide, go apostate, follow “another gospel which is not another” (i.e., false teachings), or be or be lured out of the “straight and narrow” path to eternal life and back into bondage under sin to eternal death.
The popular rendition of him as a fanciful cartoon character with horns in red tights and a pitchfork is woefully off the mark and designed again to deceive you into dismissing and underestimating the fact that he is a very real spiritual being and that he means your eternal death. The forces of evil are in a battle with the forces of God and good, and this world is the battleground. We as Christians are on the front line in this spiritual war, with Satan and the angels who sinned on one side and God and His holy angels and saints on the other side. Do not make the mistake of underestimating Satan, nor make the mistake of pretending he doesn’t exist. Both mistakes can lead you to eternal death. See also the chapter on The Armor of God.
Anderson, R. John. "6.2 Satan (The Devil) Is Just a Myth False Teaching." EachDay.org. Access date: September 25, 2023. https://eachday.org/part-vi-beware-the-wolves/6-2-satan-the-devil-is-just-a-myth/