Catalase

Melee weapon, sword, requires attunement, Wondrous

Known colloquially as “The Handheld Guillotine,” this legendary, almost Egyptian-styled curved sword deals 1d10 slashing damage with a +2 to hit and damage.

Decapitate. When you attack a creature that has at least one head with this weapon and score a Critical Hit, you cut off one of the creature's heads. The creature dies if it can't survive without the lost head. A creature is immune to this effect if it is immune to slashing damage, doesn't have or need a head, has legendary actions, or the DM decides that the creature is too big for its head to be cut off with this weapon. Such a creature instead takes an extra 6d10 slashing damage from the hit.

Adrenaline Surge. If you reduce a creature’s hit points to 0 using this weapon, your attack counter is reset and you get to take another action.