The sword is thin, but the blade is triangular rather than flat, in the fashion of many monster hunting rapiers (Piercers). The blade is segmented, and when tension is released from the cable within it, it can instantly turn into a vicious bladed whip. It takes no action to transform the blade between whip and blade form (i.e. each attack can be made with a different mode).
The vicious weapon has a +1 to damage.
Rapier Mode 1d8 + 1 piercing damage.
Whip Mode 1d4 + 1 slashing damage. Finesse, Reach (10ft, but cannot be used within 5ft)
Whip functionality
Can be used to shove, or knock prone, RAW.
Using the Attack action, you can make a special melee attack to shove a creature, either to knock it prone or push it away from you. If you’re able to make multiple attacks with the Attack action, this attack replaces one of them.
The target of your shove must be no more than one size category larger than you, and it must be within your reach. You make a Strength (Athletics) check contested by the target’s Strength (Athletics) or Dexterity (Acrobatics) check (the target chooses the ability to use). If you win the contest, you either knock the target prone or push it 5 feet away from you.