John of Damascus tells us, "Of the future both the angels of God and the demons are alike ignorant; yet they make predictions. God reveals the future to angels and commands them to prophesy, and so what they say comes to pass. But the demons also make predictions, sometimes because they see what is happening at a distance,and sometimes merely making guesses. Hence much of what they say is false, and they should not be believed, even although they do often, in the way we have said, tell what is true; besides, they know the Scriptures.

Infact, there is quite often the easiest version of demons to "summon" so to speak is to simply attempt to pray to God the Father, Christ the Son, and the Holy Spirit... demons will routinely go after people attempting to pray. The little voice in your mind saying that "you don't need to pray" or "there is no God" or "You're a good person you don't need to repent" etc... and as soon as you screw up there are also there "You're evil, you're going to burn, you are like us, you will be with us, HAHA we got you!"