i can tell you from personal experience that he and his minions can live with you for months feeding you truths and getting your trust before they do their dirty work on unsuspecting people. That's one of the major needs to know the Word of God...... and I do mean all of it.
It is very dangerous to have the idea that either Satan or any demonic entity can't tell you the truth. It is my understanding that they will not tell you that Jesus came in the Flesh and is Lord of all..... though I do not know that as a irrefutable fact.
Similarly, I think the enemy can tell you a 'truth' but not THE truth. Jesus is absolutely THE way, truth, and life. For instance, I totally accept that God lavishes abundance grace upon us. But I don't agree, as some preachers would have us believe today, that then I can continue to sin and it won't make a difference to my walk with God. Check it out:
Romans 5v19 - 6v16
19 For as by one man's disobedience many were made sinners, so by the obedience of one shall many be made righteous.
20 Moreover the law entered, that the offence might abound. But where sin abounded, grace did much more abound:
21 That as sin hath reigned unto death, even so might grace reign through righteousness unto eternal life by Jesus Christ our Lord.
6 1What shall we say then? Shall we continue in sin, that grace may abound?
2 God forbid. How shall we, that are dead to sin, live any longer therein?
3 Know ye not, that so many of us as were baptized into Jesus Christ were baptized into his death?
4 Therefore we are buried with him by baptism into death: that like as Christ was raised up from the dead by the glory of the Father, even so we also should walk in newness of life.
5 For if we have been planted together in the likeness of his death, we shall be also in the likeness of his resurrection:
6 Knowing this, that our old man is crucified with him, that the body of sin might be destroyed, that henceforth we should not serve sin.
7 For he that is dead is freed from sin.
8 Now if we be dead with Christ, we believe that we shall also live with him:
9 Knowing that Christ being raised from the dead dieth no more; death hath no more dominion over him.
10 For in that he died, he died unto sin once: but in that he liveth, he liveth unto God.
11 Likewise reckon ye also yourselves to be dead indeed unto sin, but alive unto God through Jesus Christ our Lord.
12 Let not sin therefore reign in your mortal body, that ye should obey it in the lusts thereof.
13 Neither yield ye your members as instruments of unrighteousness unto sin: but yield yourselves unto God, as those that are alive from the dead, and your members as instruments of righteousness unto God.
14 For sin shall not have dominion over you: for ye are not under the law, but under grace.
15 What then? shall we sin, because we are not under the law, but under grace? God forbid.
16 Know ye not, that to whom ye yield yourselves servants to obey, his servants ye are to whom ye obey; whether of sin unto death, or of obedience unto righteousness?
Now if we just read 5v19-21, what would our flesh tell us God is saying?
Don't get me wrong, God's Word is full of encouragement, but the whole truth isn't always acceptable to flesh. Solution: crucify flesh. And that's the truth.