Tail's End Rapier (Very Rare)

The blade of this wicked khopesh is composed of several individual sections linked by a sturdy chain running through the weapon's length. Always dry to the touch, this magical blade appears to continuously absorb any water with which it comes into contact.

Split at the Seams: As a bonus action, you can press a button hidden on the weapon's hilt to cause the sections comprising the blade to magically detach from one another, remaining connected by the chain. Until reformed as a sword as a bonus action, this weapon loses its former sword properties and gains those of a whip.

Unquenchable Thirst: When you roll a 20 on an attack roll made with this weapon, it releases a deadly burst of desiccating, negative energy that drains moisture from a target, forcing it to make a DC 16 Constitution saving throw. On a failed save, the target takes 10d6 necrotic damage and is desiccated for 1 minute. On a successful save, a creature takes half as much damage and isn't desiccated. A desiccated creature's skin turns dry and brittle, rupturing with ease, and causing the creature to take an additional 1d8 slashing damage whenever it takes bludgeoning, force, piercing, slashing, or thunder damage. A desiccated creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. This property has no effect on creatures without skin or on those immune to necrotic damage.

Finesse: When making an attack with a finesse weapon, you use your choice of your Strength or Dexterity modifier for the attack and damage rolls. You must use the same modifier for both rolls.

Proficiency: martial, rapier Source: Heliana's Guide to Monster Hunting - Part One p. 480, Player's Handbook (2014) p. 149