Oblivion

Weapon (greatsword), very rare (requires attunement)

Oblivion is a massive sword, and its blade is carved from a single piece of deep purple obsidian. Its handle is wrapped with rough straps of black leather.

You gain a +2 bonus to attack and damage rolls with Oblivion. In addition, it has 3 charges that recharge when you finish a long rest. When you hit a creature with an attack from Oblivion, you can use a bonus action to expend a charge and cast Tasha's Mind Whip at the creature.