Lovesickness Pen

The magic of deception is a tricky and expensive art to perform on command. Thus, simple enchantments of deception are typically plentiful. One common enchantment, despite it being outlawed in most towns and cities of the Mindreland, are lovesickness pens (or quills, or any other writing instrument). Anything written by the user appears normal to them but to the intended recipient will carry the opposite meaning.
A businessperson might slip such a pen into their competitor's office just before they address a letter to a potential client. Or a disgruntled father would offer his infatuated daughter the pen as a gift in hopes that the next letter she pens to her lover is their undoing. It's the later case which gives the item its infamous reputation.

History

Curiously, the pen was originally created by crooked sorcerers as a scam. Any note of adequate forgery would do just the thing but those too cowardly or scrupulous to commit the crime themselves would pay good money for an alternative.
The first pens were sold in the markets of Redgate around 800. Their rise in popularity prompted versions of the item to appear in all the continental cities where sorcerers could be found. More sophisticated pens were created, capable of detecting nuance and mimicking a writers style and a small sorcerer's craft emerged around the creation of lovesickness pens.
They were outlawed in Redgate in 822 with all other major cities following suit. But the laws typically banned the sale of the pens, not their creation, thus the sorcerers still operated in the open but the merchants who received their creations moved to the back alleys.
Notable uses of the pen are few. The third governor of Redgate was ousted from office after delivering a personal letter to a friend which spoke of his "distaste for the Marzeinians, Aposfabrians, Quiates, and every other 'invader' of the country of Nilofaur." Those who suspected the involvement of magic failed to act in time to prevent the disaster.
In 1103, tensions between the people of Namettes and the Tember Hezethal in the hills to the north were at their highest. A note delivered to the leader of the Tember detailed the Namettes refusal to compromise. Only at the end of the bloody conflict that had broken out was it discovered that a Tember spy had supplied the author with a lovesickness pen.

Mechanism

A lovesickness pen works by inverting the authors writing, not their thoughts. Illusory magic hides the effect from the author, at least for a time. These qualities make the tool a fickle item subject to variances in quality.
A well-made pen is nearly impossible for the user or recipient to detect. The penned words are grammatically sound and may even represent some of the nuance of the original writers style. A pen more simply made may contain grammatical errors or create writing that is stiff and uncharacteristic of the writer. Poorly made pens may also fail to deceive the writer, changing certain words on a second or third glance.
Detection that a lovesickness pen specifically was used is impossible as the note appears normal by the time its recipient has received it, the illusion magic having worn off. The pen itself, however, can be easily identified by a competent sorcerer.

Item type

Tool