As Satan sat pondering on his throne of human skulls he came up with an idea, he thought that since he could not stop mans belief in God, he would simply use mans pride against him, he divided religion,instilling in man that their religion was the only way to get closer to God, causing religious wars.
His second greatest trick was to blind mans eyes and heart to his excistance, once that occurred no man believed that Satan excisted, therefore had no power to corrupt.
His third greatest trick was to use Gods word against man, since all things come from God, Satan used this to make people think, all bad things came from God, not him, causing man to be angry with God.