There are up to four unique swords to find in Diablo 4, two of which are exclusive to the Barbarian class for obvious reasons.
Barbarian is the best class to make use of the unique swords you find in Diablo 4. These unique items are all about doing an insane amount of slashing damage to cut enemies down to size.
As with the other unique items in D4, unique swords will only start dropping after you have unlocked (and are playing) World Tier 3 or higher. Keep running dungeons for a chance to see them drop. Doombringer (General)
Doombringer returns to Diablo 4 as a unique sword after appearing among unique items in all of the previous three installments.
Its unique effect increases your shadow damage against all nearby enemies while reducing the damage done to you by them in return for a few seconds.
Doombringer also increases your core skill damage, critical strike damage, and overall damage to boost your shadow output.
