The Lightbringer Sword 5e

The Lightbringer Sword is a creation of the most horrible of magic users ever to live.

Lightbringer Sword (or the Harrower)

Type: Legendary magical weapon (longsword)

Description: This Short Sword has a long, curved blade with a blackened steel finish. Its hilt is wrapped in a slim, shiny leather, and its crossguard includes intricate runes on a replica of a dragon of ivory. A faint yellowish glow surrounds the blade when it is drawn.

Stats:

Attack: +2 against evil creatures
Damage: +4 against evil creatures

Properties:

Detect evil:

This sword understands and can communicate telepathically to its wielder the location of the evilest creature in sight (maximum range 120 feet).

Evil Absorption:

When the wielder of this sword strikes an evil creature, the sword absorbs part of the creature’s evil essence. This essence is stored within the sword until the sword is broken. An evil creature that drops to 0 HP by the stroke of the Lightbringer Sword loses its evil delineation. If it is stabilized or otherwise brought to life, it is confused and it will start to make amends for its past deeds (DM rules on the extent).

Evil Release:

Breaking the sword, intentionally or not, releases the evil stored within it. The sword unleashes a wave of dark energy out of the point of its damage. All evil creatures within 120 feet of the wielder must make a DC 17 Wisdom saving throw or be charmed by the wielder and become friendly to them for a year and 1 day.  The maximum CR of any evil creature killed since the last breaking point is the maximum CR of a creature that can be charmed thusly.

If the wielder of the sword knows the right rituals, she can also imbue a 120-foot cube with evil. In reality, this area acts like a “lair”. Lair actions have an initiative of 20 and it includes 2 actions that can be used once per day each.

• Trumpeting the Victory of Evil: All non-evil creatures roll a DC 20 Wisdom save, or become Desponded (see below) for 1 minute.
• Regenerate Vilain: The lair casts Regenerate on its host as soon as it detects her falling below 50% of her full HP. This is cast as a Reaction.

Attunement:

Requires attunement from a creature of non–evil alignment.

Despondent

This condition represents a sense of overwhelming hopelessness or depression. Any effect that grants a creature advantage on saving throws against being frightened also grants advantage on saving throws against becoming despondent. Similarly, a creature immune to being charmed is immune to being despondent. Casting greater restoration on an affected creature ends this condition.

-A despondent creature can’t have advantage on ability checks to interact socially.
-The creature does not add its proficiency bonus to its attack rolls or ability checks.
Source Pt-MCCbtS

Plot Hooks

The Evil Shadow Mage Mariana ensorcells the most incorruptible Paladin of the land to go forth and smite evil. She gives him the sword on a year-long loan.

The sword is the spell-focus item of the Lawful Good Hexblade Warlock. The entity from Shadowfell/ Patron will claim the sword upon the death of the Warlock. The entity may be appearing to the Hexblade to be as a creature of light and goodness so that the Lightbringer Sword gets its proper wielder.