You reach inside and pulled out...a piercing? it looked like a piercing alright, a small, smooth arc of dark gray metal decorated with a small yellow stone. It was still in the box, thank god — you didn't want to put anything in your body that had been lying unprotected in a bargain bin — and the box was labelled "Speak the Truth!" in a whimsical and, in your opinion, somewhat silly font.
"What does this do?" you asked, picking up the box and turning to the cashier.
He smiled.
"Just what it says. Truth-teller tongue piercings make anything you say the reality!"
You winced.
"Tongue piercing? Does that mean–"
"Oh, no no, don't worry about it. We're called a 'magic' shop for a reason. All you have to do is press it against your tongue, and it'll be like you always had a piercing there. No needles necessary."
"So...anything I say? Always true?" you asked, going over the possibilities in your head.
"Within limits! You can't break the universe with any of our items. Tautologous statements are rendered factual regardless of..."
He trailed off, noticing your bewildered expression.
"Sorry. I mean," he said, laughing slightly, "that you can't just say 'two plus two is five.' Things like that are true by definition. Our products can only change the parts of reality that are...malleable. Things the universe wouldn't mind changing up now and then."
You nodded. It made sense, more or less.
"So, how much for it?"
The man looked over at the bargain bin, then at the box.
"I'd say $20, for you. A word of warning though: these bargain bin items can be a bit...finicky, if you catch my drift. Stick to little truths at first, to make sure nothing's broken."
You nodded, barely paying attention to the words — twenty dollars! That little for an artifact which could warp reality? You *had* to buy it.
The clerk looked at you with a bemused expression, noticing how you barely seemed to be listening to his warning. He had his suspicions about this particular artifact. Some people with faulty truth tongues had everything they say turn out to be false, or compelled them to answer any question truthfully no matter how private or embarrassing. Still others were cursed so that anyone listening to them assumed they were lying when they told the truth, and only believed them when they outright lied. He'd had experience with many of these piercings before, but he'd long since decided it was a lot more fun to watch events play out rather than give a more intense warning. Where was the fun in a voiding chaos altogether? The customer could always get a refund.
You handed him a crisp 20, and he grinned.
"Would you like to apply it here in the store? We can recycle the packaging for you."
You nodded.
"Sure, that sounds good. So I just...take it out and press it on my tongue?"
Your voice was doubtful, but the clerk nodded encouragingly.
"Yup! Just like that."
Shrugging, you opened the box, removed the small metal bar, and pressed it carefully against your tongue.