Seeing the peril his people faced, a young dwarf prince came to believe that his people needed something to protect them. Thus, he set out to forge a weapon that would be such a weapon.
Venturing deep under the mountains, deeper than any dwarf had ever delved, the young prince came to the blazing heart of a great volcano. With the aid of Moradin, the dwarven god of creation and ten warforged, he first crafted four great tools: the Brutal Pick, the Earthheart Forge, the Anvil of Songs, and the Shaping Hammer. With them, he forged the Axe of the Dwarvish Lords and Glaive of the Sentinels.
Armed with the artifact, the prince returned to the city of Tyar-Besil. He gave the glaive to the warforged that defended the city and the king Torhild Flametongue. The glaive ended hoards of monsters attacking the city and keept the peace. When the warforged was destroyed they passed the weapon, which had become a badge of office, to the next warforged royal guard.
Later, in a dark era marked by the death of Torhild Flametongue and the complete abandonment of Tyar-Besil, the glaive was lost. Centuries later, the dwarves still search for the glaive, and many adventurers have made careers of chasing after rumors and plundering old vaults to find it.

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Magic Weapon

The Glaive of the Sentinels is a magic weapon that grants a +2 bonus to attack and damage rolls made with this magic weapon.  
While you hold the glaive you gain advantage against effects that would cause you to being Charmed and immunity to beeing Frightened

The years of sentinels have inprinted on the glaive gives the wearer a +2 bonus in Insight, Investigation and Perception.

The first time you attack with the glaive on each of your turns, you can transfer some or all of the glaive's bonus to your Armor Class, instead of using the bonus on any attacks that turn. For example, you could reduce the bonus to your attack and damage rolls to +1 and gain a +1 bonus to AC. The adjusted bonuses remain in effect until the start of your next turn, although you must hold the glaive to gain a bonus to AC from it.

Sentience. Glaive of the Sentinels is a sentient neutral good weapon with an Intelligence of 16, a Wisdom of 15, and a Charisma of 7. It has hearing and darkvision out to a range of 30 feet.

The glaive can speak, read, and understand dwarven, and it can communicate with its wielder telepathically. It knows every language you know while you’re attuned to it.

Personality. The Glaive of the Sentinels speaks with a sulky and depressed male voice. It was made to protect dwarves against all enemies and its long watch has slowly driven it in to a depression that has been growing worse by the hundreds of years it has laid alone and dormant. Conflict arises if the wielder fails to maintain a cherry disposition or is struck by great sadness. 

Proficiency with a Glaive allows you to add your proficiency bonus to the attack roll for any attack you make with it.

Notes: Bonus: Insight, Bonus: Perception, Bonus: Magic, Bonus: Investigation, Advantage: Saving Throws, Immunity: Frightened, Warforged, Damage, Control, Social, Combat, Heavy, Reach, Two-Handed, Graze