All rooms that are guaranteed to appear due to the required parts will no longer appear after turning the parts in.
Obsidian Shell Casing will always drop from High Dragun's skull, but cannot be turned in more than once.
It's not possible to go back and get the Bullet That Can Kill The Past once the player enters the Aimless Void, so if the player wants to kill their past they better be sure they have it before proceeding.
It is not necessary to carry the Bullet That Can Kill The Past to access Bullet Hell and defeat the Lich.
It is not required to carry the Bullet That Can Kill The Past to access The Cultist's past.
Bullet components do not carry over between runs, unless turned in to the blacksmith.
The Bullet That Can Kill the Past can be stolen by the Resourceful Rat.
If the player decides to use the Gun That Can Kill The Past without this item, they will still be able to shoot themselves and reach the credits screen, though their run will immediately end there instead of accessing their past.
If the main player in a co-op run dies during the High Dragun boss fight, when resurrected post-battle they will no longer have the Bullet. However, they can still shoot the Cultist or themselves with the Gun and enter the past.
The Blacksmith will not give the Bullet That Can Kill The Past if the player is playing as The Paradox.
passive item.