Infinity Blade (5e Equipment)
From D&D Wiki
Weapon (longsword), legendary (requires attunement)
You gain a +3 bonus to attack and damage rolls made with this magic weapon.
When you hit an aberration or elemental with this weapon and reduce it to 0 hit points, the creature is shattered into pieces and disintegrated, and nothing short of the wish spell can bring it back to life.
When you hit a creature with this weapon, you can cast banishment against the creature as a bonus action. The save DC for this spell is 17, or 20 if the creature is an aberration or elemental. Once you cast the spell this way, you cannot cast it again until the next dawn.