We obviously understand that Satan is a liar. The Bible says that he is that old serpent which is called the Devil and Satan which deceiveth the whole world.
The Bible describes him as being a liar and the father of it. In John 8.44, his most effective tool against mankind has been deception.
And the greatest tool that he's ever been able to propose to mankind is that somehow they can merit eternal life apart from Jesus Christ.
That they can do good works and be a good person. But even within the realm of Christianity, he's been able to deceive people into thinking that
believing on Jesus for salvation is not enough. That somehow the sacrifice of Christ is insufficient.
That we have to participate in our salvation via repenting of our sins, keeping God's commandments, having a relationship with Jesus.
And that somehow our integration of our righteousness along with the righteousness of Jesus will get us saved.
But the Bible says not by works of righteousness which we have done, but according to his mercy he saved us.
And what people fail to realize is when the Bible says believe on the Lord Jesus Christ and thou shalt be saved, that is at the exclusion of our works and our obedience.