Silverwind, the Cleansing Breeze

This mighty longsword once belonged to Syre, the fey lord of the now fallen Syre Wood. This ancient blade was used to lead the charge against a legion of invading fiends, and still holds a power over such creatures. You gain a +1 bonus to attack and damage rolls made with this magic weapon, which has the finesse property. When you hit a fiend with an attack using this sword, that creature takes an extra 1d6 radiant damage.

Instant Attunement. If you pull Silverwind, the Cleansing Breeze from the body of Malfuriel the Betrayer, you are immediately attuned to it. When this happens, you can choose to immediately end your attunement to one of your other magical items, even if it’s cursed (as if by the remove curse spell or similar magic). If you are already attuned to your maximum number of magic items, you must end your attunement to one of them in this way.

Variant Properties. Some properties of this artifact are locked behind layers of dormant magic. As you grow stronger and reach certain milestones, these properties may become available to you. This weapon can have up to 3 of the following properties active at a time. When you attune to Silverwind, up to the first 3 properties available to you are activated. Whenever you finish a long rest, you can replace any of the activated properties with another one.

While holding this sword, you can use an action to cast the dancing lights, druidcraft, or minor illusion spell (save DC 13) from the weapon. In addition, when you reach 5th level, you can use a bonus action to cast the true strike spell from it.

Prerequisite: Fey Ancestry trait or the fey creature type. You are immune to disease.

Prerequisite: 8th level. Your bonus to attack and damage rolls with this weapon becomes +2, and any fiend hit by it takes an extra 2d6 radiant damage, instead of 1d6. When you reach 14th level, the bonus increases to +3, and any fiend hit by it takes an extra 3d6 radiant damage instead.

Prerequisite: 8th level, Fey Ancestry trait or the fey creature type. You can use an action to touch a creature and magically know its current emotional state. If the target fails a DC 16 Charisma saving throw, you also know its alignment. Celestials, fiends, and undead automatically fail the saving throw.

Prerequisite: 14th level. While holding this sword, you can use a bonus action to create an illusory copy of yourself in an unoccupied space you can see within 30 feet of you. You choose what direction your copy is facing. The copy mimics your movements and attacks with this sword until the end of your turn, moving forward, turning, and attacking to match your actions relative to its position. The copy can't walk through walls or other solid surfaces. The copy uses your attack and damage rolls for any attack you make with this sword, dealing force damage instead of slashing on a hit. The copy vanishes at the end of your turn. If the copy is in an unoccupied space when it vanishes, you can choose to teleport to its space. Once this property of the sword has been used, it can’t be used again until the next dawn.

Prerequisite: 14th level, Fey Ancestry trait or the fey creature type. While this sword is on your person, you can use an action to cast the disguise self spell (save DC 16). If you drop the sword, the spell ends.

Prerequisite: Slay or help slay Malfuriel the Betrayer or similarly powerful fiend. When you attack a creature with this weapon and roll a 20 on the attack roll, that target must succeed on a DC 16 Constitution saving throw or be magically restrained until the end of your next turn. If the target is a fiend, it's petrified until the end of your next turn instead.

Prerequisite: 20th level. You gain the benefits of all of this sword’s variant properties, including those whose prerequisites you don’t meet.

Destroying Silverwind. The only way to destroy Silverwind, the Cleansing Breeze is to melt it in the fires of the Magmarath Caldera, a raging volcano in the Lower Planes overrun with fiends. It must remain submerged in the magma for 10 years before it succumbs to the fire and is destroyed. When it does, the volcano erupts.