You found a magic item!
The Age of Decadence is a time period where finding magic items is so extraordinary that the mere discovery of written scripture regarding one instills a sense of wonder and amazement, even to experienced adventurers. It is said that in the ages past great instruments of power were forged by both holy and unholy means, yet almost all are forgotten to the annuls of time. Legends speak of some that could break the fabric of reality and have long since been destroyed. Much to the dismay of the masses is it believed that many still exist, even after the Sundering brought life on Terratus to near extinction. Some have only minor effects while others can give a single person power enough to destroy entire cities. Whatever the case may be, they always bring danger to the user for in the region known as the Tiers, magic in all its forms is looked upon as a menace by the majority and an opportunity by those who would seek to harness it.
Soul Crystal of a Gargoyle
Wondrous item, artifact (requires attunement)
As an action this crystal can absorb the soul of a newly slain creature and can only hold a single soul. A fresh soul provides 2 charges and it can only be used once per long rest. A new soul can replace a partially used soul but it will not refresh its use based on rests, it will only replace the charges. The level of spell able to be cast below depends on the strength of the absorbed soul, when absorbing a soul ask the Dungeon Master what level of power the soul provides.
As an action you can utilize this artifact as a spell casting focus and cast any known spell of the specified level as a bonus action and can follow up with a regular spell of any level so as long as it is not the same spell cast previously.
"A remarkably intact soul crystal found within a gargoyle of the old times. The Soul Arts are from a forgotten age when great rulers used the powers of souls to shape the world but if they were so great, where are they now? Their creations lie swallowed up in the darkness and the crystals of the Soul Arts are a mystery that hold many unbroken secrets.
It is a sign of luck that you only encountered a lesser gargoyle to obtain this. Gargoyles themselves are said to be sentries created by the sorcerer kings of old. Some were originally made to guard the interior of high holy places and others were said to watch important places of commerce. Since then gargoyles have been rumored to have taken many forms in all the ancient and destroyed empires throughout history and are especially known to guard castles and forts from ill fortune."
