The Heavy Arrows is a passive item found in Momodora: Reverie Under the Moonlight. It's one of the best items in the game if the player prefers to use the bow instead of the leaf.
The Heavy Arrows can be obtained by defeating Duchess Lupiar and Royal Huntress Magnolia without taking any damage. These are two sequential boss fights, taking damage in any of them will cause Magnolia not drop the item at the end.