In Christian tradition, the "ancient serpent" is commonly identified with the Genesis' Serpent and as Satan.

I came upon the Garden like the ancient serpent, intent upon exploiting the inherent corruptibility of man.

The great dragon was hurled down--that ancient serpent called the devil or Satan, who leads the whole world astray.

The Book of Revelation twice refers to "the dragon, that ancient serpent, who is called the devil and Satan," (12:9, 20:2).

Virissong's sacrifice was to Amhuluk, the ancient serpent, not for his Enemy.

An ancient serpent with seven heads who lives in a cave.

After defeating several powerful goblin leaders, Sayo must battle their leader, the ancient serpent Orochi.

Because he hadn't abandoned me after I'd thrust him out of the Dead Zone when I faced the ancient serpent there.

No, nor do I. The lives of ancient serpents are not a part of our daily existence.

I command thee, ancient serpent, to depart from hence.