Revive banished Metaphys monsters for more field presence or when pushing for damage. When the Metaphys monster returns to your hand, you can Normal Summon it the next turn if you have Metaphys Factor.
Recycles banished Shiranui monsters. You can revive a banished Shiranui Spectralsword for Synchro plays. You can also revive Shiranui Solitaire and tribute it to Special Summon Shiranui Spectralsword from the deck.
Budget version of burial from different dimension but more aggressive because it will special summon means you can attack with that monster. Not to mention you can revive your opponent monster as well. Back to the hand is somewhat good for discard fodder or normal summoned only effect.
Dark Cavalry doesn´t have any effect that allows him to return from the Banished zone. If you are wondering why you couldn´t stop that from happening with his ability: FL Every doesn´t target with her banishing ability, so Dark Cavalry can´t activate his ability as response.