You gain a +3 bonus to attack and damage rolls made with this magic weapon. 

Attunement: The sword allows you to attune to it immediately, without having to take a short rest. While attuned to it you gain the following benefits:

Magical Aura: While you hold the drawn sword, it creates an aura in a 10-foot radius around you. You and all creatures friendly to you in the aura have advantage on saving throws against spells and other magical effects. If you have 17 or more levels in the paladin class, the radius of the aura increases to 30 feet.

Truesight: Your eyes glow a fierce yellow. You can see in normal and magical darkness, see invisible creatures and objects, automatically detect visual illusions and succeed on saving throws against them, perceive the original form of a shapechanger or a creature that is transformed by magic, and see into the Ethereal Plane, all within a range of 120 feet.

Watcher's Light: The sword sheds bright light in a 5-foot radius and dim light for an additional 5 feet. Fiends find the sword’s light disconcerting and painful, even if they can’t see it, and have disadvantage on attack rolls made within the weapon’s radius of bright light.

As a bonus action, you can intensify the sword’s light, causing it to shed bright light in a 15-foot radius and dim light for an additional 15 feet, or reduce its glow to its normal intensity.

Watcher's Radiance: The sword deals an extra 9 (2d8) radiant damage to any creature it hits, or 16 (3d10) radiant damage if you’re wielding the weapon with two hands. 

Watcher's Accuracy: This weapon's damage can overcome resistances. Any damage which would have been resisted will become regular damage.

Watcher's Grave: Witnessing an ally's last breath has empowered you. As a reaction to an ally reaching 0 hit points within the aura, you can say the keywords and with the power of the watchers return the ally's health to the maximum. This effect can only be used once per long rest.

Watcher's Gift: Once per dawn the creature can cast a Spell of the Divination School up to the 9th level.

Random Properties: The sword has 2 minor beneficial properties, each determined by rolling on the Minor Beneficial Properties table in chapter 7 of the Dungeon Master Guide.

 Properties:  While attuned to the artifact, you can use an action to cast one 2nd-level spell Aid from it. After you cast the spell, roll a d6. On a roll of 1–5, you can’t cast it again until the next dawn. You have resistance against Fire.

 

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

Notes: Bonus: Magic, Advantage: Saving Throws, Sense: Truesight, Damage: Radiant, Resistance: Fire, The attuned creature may use it's action to cast a Spell of the Divination School up to the 9th level., Paladin, Damage, Combat, Warding, Versatile, Sap