Uh, Yes Lucifer (Shining One) Is Absolutely The Devil:
“How you are fallen from heaven,
O Lucifer, son of the morning!
How you are cut down to the ground,
You who weakened the nations!
For you have said in your heart:
‘I will ascend into heaven,
I will exalt my throne above the stars of God;
I will also sit on the mount of the congregation
On the farthest sides of the north;
I will ascend above the heights of the clouds,
I will be like the Most High.’
Yet you shall be brought down to Sheol,
To the lowest depths of the Pit.
• Isaiah 14:12-15
And He's also talked about in Isaiah 27:1
In that day the Lord with His severe sword, great and strong, Will Punish Leviathan The Fleeing SERPENT,
Leviathan That Twisted SERPENT;
And He will slay the reptile that is in the sea.
It All Comes Together in Revelation:
And war broke out in heaven: Michael and his angels fought with the dragon; and the dragon and his angels fought, but they did not prevail, nor was a place found for them in heaven any longer. So the great dragon was cast out, that serpent of old, called the Devil and Satan, who deceives the whole world; he was cast to the earth, and his angels were cast out with him.
• Revelation 12:7-9
Now when the dragon saw that he had been cast to the earth, he persecuted the woman who gave birth to the male Child.
• Revelation 12:13