Call and Response

Weapon (dagger and rapier), legendary (requires attunement)

This pair of weapons count as a single item for the purposes of attuning to them. Call, the rapier, is ornamented with musical motifs. Response, the dagger, is embossed with the visage of a singer. Together, the two weapons work in tandem. You are considered proficient with Call even if you lack proficiency with rapiers.

You gain a +2 bonus to attack and damage rolls made with these magic weapons. While holding either of the weapons, you can use an action to magically sense the direction and distance of the other weapon, provided you're on the same plane of existence. Whenever you draw Call, you can choose for Response to magically vanish from its location and reappear in your other hand (provided it's free) or in your space; while Response is in your space and not being held by you or stowed on your person, it floats around you and can't be held by another creature. Until you stow Call, you can draw the floating Response as if it were on your person, or release it in your space. Response magically returns to your space immediately after you make a ranged attack with it, provided you're holding Call.

Battle Songs. While typical blades slice through the air, Call and Response sing through it; they also harmonize. Once on each of your turns when you make an attack with Call, you can choose which Battle Song for it to sing: a Dirge of the Forgotten or Hymn of the Heavensent. The song continues until the start of your next turn.

Dirge of the Forgotten. You can immediately make an attack with Response using a bonus action. On a hit, the target takes an extra 3d6 radiant damage from the attack.

Hymn of the Heavensent. Response sweeps through the air around you, deflecting incoming attacks: you gain a +2 bonus to AC until the start of your next turn or until you make an attack with the dagger.

Warring Duet. While holding both of the weapons, you can use an action to speak their command word ("Begin," in Elvish). When you do, the weapons leap from your hands. Choose up to five different creatures that you can see within 30 feet of you: Call and Response then magically fly to each creature and make a special melee attack against them, using your attack bonus as if you were wielding the weapons. On a hit, a target takes 8d8 radiant damage and glows with a heavenly light until the end of your next turn. For the duration of the light, attack rolls against a glowing creature are made with advantage, and such a creature's attack rolls against you are made with disadvantage. After the final attack, Call and Response magically fly back to your hand and side, respectively. You then choose a Battle Song. Once this property of the weapon has been used, it can't be used again until the next dawn.

To my love: may we never know a day without each other's music.
— Engraving on the rapier Call's blade