Sword of Volsung

Weapon (longsword or greatsword), very rare (requires attunement by a fighter or paladin)

Legends tell of a dragon whose hide was impenetrable and so robust that only a blow to the heart would kill it. An unnamed hero finally defeated it and tore its heart into two. The dragon’s name was lost, but its legacy remains. This sword is one of two items that were crafted to hold its heart. The black blade is adorned with glittering silver runes, and its guard has a shallow opening at the center with grooves connecting it to the first rune. The sword’s pommel is a large, clear crystal held fast by silver scales.

You gain a +2 bonus to attack and damage rolls made with this magic weapon. When you hit a dragon with an attack using this sword, that creature takes an extra 1d6 slashing damage.

Runes of Courage. You can’t be frightened while holding or carrying this sword.

Fragment of Gram Awakened. You can use a bonus action to awaken a fragment of the spirit of the great wyrm that inhabits this blade. For 24 hours, you gain a +3 bonus to attack and damage rolls with this magic sword, and when you hit a dragon with an attack using this sword, that creature takes an extra 3d6 slashing damage. Once used, this property can’t be used again until 3 days have passed.

If you have performed the Dragon Heart Ritual, you can use a bonus action to expend 2 of the sword’s charges to activate this property, and you can use this property as often as you want, as long as you have the charges to do so.

Dragon Heart Ritual. If you are also attuned to the locket of dragon vitality, you can drain 3 charges from the locket into the sword, turning the crystal pommel a deep red and rendering the locket broken and irreparable. Doing this requires a long rest where you also re-attune with the newly charged sword of volsung.

Upon completing the Dragon Heart Ritual, the sword contains all remaining charges from the locket, and you gain the locket’s effects while holding or carrying the sword. When you are reduced to 0 hit points and trigger the locket’s temporary hit points, the sword isn’t destroyed, but you can’t trigger that effect again until 24 hours have passed.

The sword regains all expended charges after you slay any dragon. For the purpose of this sword, “dragon” refers to any creature with the dragon type, including drakes and wyverns.