The term "demerit" typically refers to a mark of punishment or a negative point given to a student for breaking rules or misbehaving.
Perhaps you're thinking of the Philosopher's Stone (or the Sorcerer's Stone in the US version), a powerful magical object that has several demerits associated with it, such as:
* Highly coveted: The Stone's power to create gold and grant immortality made it extremely desirable and a target for thieves and dark wizards.
* Dangerous: The Stone's power could be corrupted or abused, leading to negative consequences if it fell into the wrong hands.
* Tempting: The Stone's ability to grant immortality could lead to greed, selfishness, and an obsession with power.
The Philosopher's Stone itself isn't inherently "bad," but its immense power and the potential for misuse created various risks and challenges.
Let me know if you had something else in mind, and I'll try to help!