What is the Qareen and where is it located, and does it affect a believer strong in faith, and what happens to it when one says, "I seek refuge in Allah from Satan, the rejected"?

The Qareen (companion) is the devil, and he whispers to man, seeking to mislead him. The Qareen can be a disbeliever, even if the person is strong in faith. If a Muslim seeks refuge from the devil or engages in remembrance (dhikr), the devil retreats and falls back. Allah has commanded us to seek refuge in Him from the promptings and presence of devils. The devil places his snout on the heart of the son of Adam; if he remembers Allah, the devil retreats, and if he forgets Allah, the devil swallows his heart. Seeking refuge in Allah is to seek His protection from the evil of the devil, for none but Allah can restrain him from man. The remembrance of Allah protects the servant from the devil, making the devil shrink until he becomes like a fly, whereas heedlessness enables the devil to gain control over the heart.