Haelfbane

When Surtym was felled by Gilindrea Helfast all that was left was his vicious red maul, pulsing with glowing magma. The large mace was given the name Haelfbane by those left after the legendary fight between Gilindrea and Surtym, for as he left this plane in his demise, he struck out with the crimson mace and crushed Gilindrea up against a nearby mountainside. In the time since, the mace seems to arise every century or so, choosing a tyrannical individual to be its wielder. The mace holds a low level on sentience, urging its wielder to seek out nearby giant kind in order to incite them to battle. Many giants believe that the mace holds the key to the return of their lord. The latest wielder was a stonekin woman with an unknown name and origin. She roused a group of flame giants that lived within the mountains that surround the Alboldir Valley, and led them into the Expanse.

Properties

At first Haelfbane will speak to its new wielder in dreams, urging them to evil acts. When the wielder commits an act of evil that is enough to stain their soul, the weapon will feel it and awaken. The weapon is bloodthirsty, pushing its wielder to not back down from any challenge and reply with bloodshed to any insult. The weapon bestows incredible strength upon the wielder, and can make them larger for short periods of time. Additionally, the wielder knows if there are giants within one mile, and allows the wielder to send out a summons for all giants within that radius. If the wielder does not follow the will of the weapon, Haelfbane is able to withhold some of its power.

In 5e

Haelfbane

Weapon (Maul), legendary (requires attunement, cursed)
Dormant: Haelfbane increases the wielders strength by 1. When you hit with an attack, it deals an extra 1d6 fire damage.
When you sleep, you are plagued with dreams of committing terrible acts, and you gain the following flaw: I am quick to anger.
Awakening the weapon: The weapon will awaken if its wielder commits a heinous act that would stain thier soul, such as killing an innocent. It was also awaken if an individual of evil alignment that the weapon deems worthy holds on to it for a week.
Awakened: After Haelfbane has been awoken your strength score increases to 22. When you hit with an attack, it deals an extra 2d6 damage of your choice (fire, cold, lightning, or thunder). Additionally, once per long rest you may increase your size by 1 for one minute. This allows you to make strength checks with advantage, you gain 20 temporary hit points, and your melee attacks deal an extra 1d8 damage.

Haelfbane also allows you to call to nearby giants and sense their location. If you speak the command word "Haelf," you know if there are any giants within a mile and how many, but not their exact location. Once per long rest you may send out a "summons" to all giant's within the area. They are not compelled to answer the call, however they know that the summons comes from whoever is currently wielding Surtym's weapon.

Curse: The weapon can force its will on the wielder for split decisions. In order to resist, the creature must succeed against a DC 17 Wisdom saving throw.

Item type

Weapon, Melee