Tail feather from the golden rooster Víðópnir
Lævateinn was forged in the underworld by Loki (who of the Æsir is the one most associated with dwarves) near the doors of death itself, spoken of in the very late Eddic poem Fjölvinsmál. Some historians believe its translation ends with ‘wounding wand’ while others claim it is ‘wounding twig’, similar to the word for magic staff (gambantein). Either way it is this weapon and this weapon only that can kill the golden rooster Víðópnir (which sits in the branches of Yggdrasil and may be tied to Ragnarök, or possibly be another name for Gullinkambi) so that its wing joints (the only things that will suffice) can be used to distract the dogs guarding the flame-encircled castle holding Menglöð, a maiden fated to be married to the hero Svipdagr. The runed weapon awaits within however, protected by the jötunn Sinmara (a storm giant ) who will only exchange it for a tail feather from the golden rooster—that can only be harmed by the very same sword, creating a paradoxical task. Its forger and the owner of the chest that contains it can reveal the secrets to bypassing the 9 locks holding its prison closed, although Loki would only ever do so if a cunning price is attached...
Until you are attuned to this staff, it appears to be a rotting quarterstaff or battered longsword. After you have attuned to it however, runes glow along the length of the wood or the blade.
This staff can be wielded as a magic quarterstaff that grants a +3 bonus to attack and damage rolls made with it. While wielding it, you can use a bonus action to transform it into a magic longsword or back.
The staff has 10 charges for the following properties. It regains 1d8+4 expended charges daily at dawn. If you expend the last charge, roll a d20. On a 1, the staff loses its properties and becomes a nonmagical weapon (whichever form it is in when the last charge is expended).
While it is in staff form, the runes grant access to magic.
Spell Runes. You can use an action to expend 1 or more of the staff’s charges to activate a rune and cast one of the following spells from it (spell save DC 18, +10 to hit with spell attacks): hideous laughter (1 charge), speak with animals (1 charge), pass without trace (2 charges), dispel magic (3 charges), speak with plants (3 charges), confusion (4 charges), glibness (8 charges). You can also use an action to cast the charm person , disguise self , or vicious mockery spells from the staff without using any charges.
While it is in longsword form, the runes channel magic with less finesse and unleash lethal energies.
Death Rune. You can use a bonus action and 1 charge to activate this rune, causing shadows to flow out from the weapon for 1 minute. These shadows reduce dim light in a 40-foot radius to darkness , and bright light in a 20-foot radius to dim light. While the weapon is shadowed, it deals an extra 2d6 necrotic damage to any target it hits. The shadows last until you use a bonus action to speak the command word again, the duration expires, or until you drop the weapon.
Flame Rune. You can use a bonus action and 1 charge to activate this rune, causing flames to erupt from the weapon for 1 minute. These flames shed bright light in a 40-foot radius and dim light for an additional 40 feet. While the weapon is ablaze, it deals an extra 2d6 fire damage to any target it hits. The flames last until you use a bonus action to speak the command word again, the duration expires, or until you drop the weapon.