The Teeth of St. Jude

Hail Mary Doesn't Quite Cover It...

"Most holy Apostle, St. Jude," he begins, clutching a single human tooth in his hand. With nothing left for ammunition, he turns to a higher power. He ignores the creature before him as it snarls. He's afraid. Every glimpse at its yellow-gray flesh, jagged fangs, and catlike posture fills him with dread. He closes his eyes. His thoughts remain on the tooth, "the faithful servant and friend of Jesus, I place myself into your hands at this difficult time."
He opens his eyes, stares the creature down, and drops the tooth in the barrel of his 12 gauge, "Help me to know that I am not alone. Please pray for me, asking God to send me comfort for my sorrows, bravery for my fears, and healing for my suffering."
The creature's body tenses up, preparing to jump and make the kill. He tries not to think about its hideous form, the red glow in its eyes, or the sickening stench that flowed from it. He points the shotgun at the creature, "Ask our loving God to strengthen my faith and give me the courage to accept His Will for my life."
He prepares to squeeze the trigger, "Thank you, St. Jude, for the hope you offer to all who believe in you. Amen."

Faith is a curious thing. It matters very little whether one is right or wrong. What matters is the strength of their belief. The Gift of Tall Tales is a prime example of this. With enough belief, the most improbable things can become fact.
There are those in The Web who report a strange occurrence during their many operations. They stumble upon a human tooth, one that beckons to be retrieved. They hold it into the light and wonder why they feel so safe.
At one's most desperate hour, the most hopeless situation, they clutch onto the tooth and make a final stand. They survive. They may feel the urge to load the tooth into their weapon. Miraculously, the weapon fires, and the shot will always turn the tide.

History

There are few accounts of the teeth being used in history. The oldest and most well-known surviving record dates back to 1348. A hunter in the woods stumbles upon a tooth of St. Jude and ties the tooth around an arrow. The arrow was a good luck charm to the Hunter, who carried it everywhere they went.
Sometime later, the hunter found themselves face-to-face with one of the many horrors that lurk in the dark corners of the world. His weapon did nothing to avert the threat. He fired one after another, each arrow bouncing off of the creature's thick skin.
When he finally came to his lucky arrow, he aimed and let it fly. What followed was a deafening sound as the arrow flew forward at speeds much higher than an arrow could possibly go. The creature, the trees, and other obstacles behind the creature were torn apart from the force of the arrow.

How it works

The teeth of St. Jude can only be used in the most dire of circumstances. They must be the last ditch effort used in a final moment of defiance. All other options must be exhausted for the power to manifest. One does not need to be Catholic, or even know who Saint Jude is, but they must have faith.
In what could be their final moments, they must believe they will come out on top. It's not as simple as stating the fact. One must deeply feel it. They walk a line somewhere between knowing it is true and hoping it is true. If these requirements are met, the tooth can be placed in the barrel of a firearm or tied to an arrow. Should the gun be fired or an arrow released from a bow, the tooth will activate.
Activation can mean different things depending on the situation. The tooth may increase the force and speed of impact, or gain elemental qualities that are advantageous given the situation. It can also cause a chain reaction of events that lead to a favorable outcome, functioning as a simple bullet, but it will ricochet if surrounded by multiple opponents, killing them.

Rare Relics

Finding a tooth is rare, and it should be used with caution as each tooth can only be used once. They seemingly appear out of nowhere, vanishing without a trace once used. It is estimated that only a handful appear every few years.
No matter where they appear, the individual meant to take it will notice it immediately. The only person who can use the tooth would be the one who initially obtains it. If stolen, the tooth is rendered inert and can no longer be used. The teeth are considered priceless relics. Even if there was a way of selling them, they would be useless after doing so.
These rare items are sought after by many who find themselves hunting in the wild far from civilization, but these individuals are rarely the ones who obtain them. Those likely to find a tooth of St Jude include individuals who are religious or spiritual. The specifics behind these beliefs are irrelevant. One's faith is the primary factor and whether they will receive a tooth. Beyond that, not much else is known about the selection process and who or what could be behind the process.