This card can be combo with "Falling Down", since the requirement for it is to have an "Archfiend" card on the field. Even if this card if being treated as an Equip Spell Card, it is still an "Archfiend" card.
This card can be helpful in the Summoning of Rank 6 Xyz Monsters, as its effect will still trigger when its detached, since it'll still go to the Graveyard regardless, thereby activating it.
This card can be combined with "Power Tool Dragon", so that every time "Archfiend of Gilfer" gets sent to the Graveyard by the effect of "Power Tool", it can be brought back, thus creating a powerful defense.
Note that the ATK of "Power Tool" will be 1800, so leave it in Defense Position or increase its ATK with Equip Spell Cards.