Magnetism is one of the most underestimated threats in horology, an invisible force that quietly wreaks havoc on the precision of mechanical watches. Unlike knocks, water, or scratches, it leaves no obvious trace—yet a single encounter with a magnetic field can send a timepiece running wildly fast, slow, or even stop it altogether. Dubbed the hidden assassin of accuracy, magnetism is all around us in daily life, from smartphones and laptops to handbags and speakers, making it an ever-present danger that many collectors overlook until their watch falls victim.