Elis'vor, the Incandescent (5e Equipment)
From D&D Wiki
Weapon (glaive), legendary (requires attunement from a Lawful/Neutral Good aligned character)
An exquisitely crafted blade, Elis'vor's shaft is the purest white that cannot be dirtied, an intricate pattern that glows like the morning sun decorates the entirety of the shaft, the blade itself is a brilliant sunlit gold that emits a radiant glow.Upon entering the Underdark the blade emits dim-light in a 20 foot radius. The weapon always feels comforting and warm to the touch. You have a +3 bonus to your attack and it deals an additional 1d10 radiant damage upon successful hits.
If the weapon senses that its owners alignment has shifted or they no longer want to fight against evil, Elis'vor will become dormant and all abilities from the blade will not function until the owners alignment is back within the required parameters or retake up the fight against evil.
Incandescence If the wielder critically strikes, takes 40 damage from a single attack/spell or is struck by 3 different opponents in one round. You may invoke the true power of Elis'vor and it becomes incandescent. The blade emits a burst of intense radiant light, hostiles caught in a 30 foot radius must succeed a DC 20 saving throw or be blinded for 3 rounds of combat additionally all hostile entities take 3d10 radiant damage. The blade for the next 10 minutes gives off bright light in a 30 foot radius and dim light an additional 30 feet beyond. The weapon also deals 3d6 radiant damage instead of 1d10 on successful strikes. If the owner fall unconscious or is killed then the blade reverts back to its standard form.
Know thy enemy Elis'vor has spent its entire creation hunting creatures of an evil nature and their weaknesses. If the user manages to land an attack on any creature that is inherently evil the creature must then make a DC 17 Constitution saving throw. On a failed save, Elis'vor's divine senses telepathically inform the wielder of the type of entity and its immunities, resistances and weaknesses they have just struck. This feature only triggers once per turn.
Only the Unholy If the wielder attempts to kill any entity whose alignment is Lawful/Neutral Good, then Elis'vor immediately causes its owner to miss. If this occurs 3 times, then the wielders alignment shifts to Neutral and Elis'vor unbinds itself and deals 6d10 radiant damage. The owner can never re-attune to the weapon and if they continue to try and use it as a normal weapon Elis'vor punishes them resulting in disadvantage on all attack rolls.
Fear the Eye Due to the history of the soul inside, Elis'vor has an innate fear of beholders and will cease to communicate until the being is out of sight or dead. Negating the Know thy enemy ability, Elis'vor's pain and suffering inflicts the user with disadvantage on Wisdom saving throws and Concentration checks while within visual range of a beholder. Upon first seeing a beholder the wielder's vision immediately goes into a flashback of some of the most horrendous torture inflicted upon Elis'vor. This causes the owner to recoil in the shared pain and they have to make a DC 17 wisdom saving throw, on a failed save the wielder takes 2d6 psychic damage.
If Elis'vor achieves the killing blow upon a Beholder then it does not suffer the penalties of Fear the Eye.