Cursive

Weapon (rapier), legendary (requires attunement)

This blade features the motifs of a fountain pen. Its guard is seemingly made of a swirling plume of ink but is solid as metal to the touch. You gain a +2 bonus to attack and damage rolls made with this weapon, or a +3 bonus if you're proficient with calligrapher's supplies.

A creature hit with the weapon takes an extra 2d4 acid damage: the creature gains one cumulative mark for every 4 you roll on the d4s. A mark appears as a dark, inky blotch where the creature was hit. For every third mark a creature receives, it must make a DC 17 Constitution saving throw. On a failed save, the creature is stunned until the end of your next turn. On a successful save, the creature's speed is halved until the end of your next turn, and it has disadvantage on the next attack roll it makes before then. A mark remains for 1 minute before magically dissolving.

Pen Form. While holding Cursive, you can use a bonus action to magically transform it into a fountain pen or back into a rapier. While it's a pen, it produces its own ink as you write with it. The ink is nonmagical.

Illusory Script. You can use an action to cast the illusory script spell from the weapon (in either form), using the tip of the pen or blade to write the message. You can have up to three messages written in this way at a time. If you make a fourth message, the first one disappears.

Stunning Symbol. You can spend 1 minute using the rapier to draw a symbol on the ground, duplicating the effects of the symbol spell (save DC 17; Stunning option only). Until the symbol is dispelled, the rapier ceases to deal its extra acid damage. The symbol is dispelled automatically whenever you finish a long rest. You can only have one symbol in this way at a time.

The pen is mightier than the sword, they say, but together, they're stronger still.