The Mourning Blad

Weapon Magical, Heavy, Two Handed Legendary (this item requires attunement) [Lawful Evil]

The Mourning Blade, created by Mephistopheles himself, is a blade powerful enough to strike down gods where they stand. Those who are killed by the blade have their soul trapped in there forever. The first time the blade was used was against the goddess I'llvana, where her soul is now stuck. Every time a soul is taken, the user can faintly hear a feminine voice softly weeping, which is believed to be I'llvana herself. The user must make a Wisdom save DC of 15. On a save they attack normally. On a failed save they hear the cries of all the lives the sword has taken and will have disadvantage on their next attack. Once attuned to the item, the user no longer lets the cries of the fallen impose disadvantage.