[RPG] Is this homebrew whip blade balanced

dnd-5ehomebrew-reviewweapons

One of my players has asked if he can have his character use a whip blade (i.e., a sword that transforms into a whiplike chain to deal damage at a distance). See here for a picture. Based on my discussions with him, he would like to start with this weapon.

Whip Blade
Martial Melee Weapon

Cost: 50 gp
Weight: 3 lb
Damage: 1d6 slashing
Properties: Special

When using a Whip Blade, you may interact with it to toggle between solid blade form and whip form. In blade form, the weapon has the Finesse property. In whip form, the weapon has the Reach property, but attack and damage rolls using this weapon must be made using your Dexterity modifier.

My hope is to create a weapon that is balanced (i.e., neither strictly better nor strictly worse) relative to the other martial weapons in the table in the PHB (pg. 149). What changes need to be made for this to be the case?

Best Answer

The whip blade is unbalanced for dexterous characters and pointless for strong characters.

(I am assuming that the interaction to toggle forms is completely free because no action is mentioned in the whip blade's description)

Toggling forms

In most cases, a character can change their reach once during their turn by dropping a weapon and unsheathing another weapon that has more or less reach.
By comparison, the whip blade can toggle its form to change the reach as many times as necessary per turn without the hassle of dropping stuff onto the ground. I think that the toggle ability is decent in the hands of a tactical player, but not game changing.

Dexterous characters (dex ≥ str)

The whip form's lack of finesse is inconsequential because the whip form uses dex anyway.
The whip form is strictly better than whips because of the extra damage.
The whip form is at least on par with rapiers and scimitars. However, if the dexterous character has the dual wielder feat then the whip form is strictly better than scimitars.
Moreover, the whip form is strictly stronger than the blade form too, so the toggle ability is useless outside of some really rare scenarios where having reach is a negative.
Overall, I would almost always use the blade whip with a dexterous character over any other melee weapon.

The exception are rogues because they need the finesse property for sneak attacks. However, rogues are not proficient with whip blades, so it's not worth analyzing.

Strong characters (str > dex)

The finesse property is meaningless to strong characters and so the blade form is strictly worse than all one-handed martial melee weapons except for the whip and the lance, and generally worse than all martial melee weapons.
The whip form is strictly worse than whips when you consider the reduced chance to hit from using dex instead of str.
Overall, I would almost never use the whip blade with a strong character.

My recommendation

Just flavor a regular whip to be a whip blade. When the enemy is within 5' describe the attacks as belonging to a solid blade, else describe the attacks as belonging to a whip-like sword. Guaranteed balanced.

Once the game progresses to the point that magic weapons are available, put something like this in the loot.

Whip Blade
Weapon(whip), rare

You have a +1 bonus to attack and damage rolls made with this magic whip. When you make an attack with it during your turn, you can forgo its reach property to deal an extra 1d4 slashing damage.