Christ taught that Satan was a real person

Luke 10:18

He replied, “I saw Satan fall like lightning from heaven.

Revelation 12:7-12

7 And there was war in heaven. Michael and his angels fought against the dragon, and the dragon and his angels fought back.

8 But he was not strong enough, and they lost their place in heaven.

9 The great dragon was hurled down—that ancient serpent called the devil, or Satan, who leads the whole world astray. He was hurled to the earth, and his angels with him.

10 Then I heard a loud voice in heaven say: “Now have come the salvation and the power and the kingdom of our God, and the authority of his Christ. For the accuser of our brothers, who accuses them before our God day and night, has been hurled down.

11 They overcame him by the blood of the Lamb and by the word of their testimony; they did not love their lives so much as to shrink from death.

12 Therefore rejoice you heavens and you who dwell in them! But woe to the earth and the sea, because the devil has gone down to you! He is filled with fury, because he knows that his time is short.”

Revelation 13:1-4

1 And the dragon stood on the shore of the sea. And I saw a beast coming out of the sea. He had ten horns and seven heads, with ten crowns on his horns, and on each head a blasphemous name.

2 The beast I saw resembled a leopard, but had feet like those of a bear and a mouth like that of a lion. The dragon gave the beast his power and his throne and great authority.

3 One of the heads of the beast seemed to have had a fatal wound, but the fatal wound had been healed. The whole world was astonished and followed the beast.

4 Men worshiped the dragon because he had given authority to the beast, and they also worshiped the beast and asked, “Who is like the beast? Who can make war against him?”