I lean on a lot of SCP-like themes and this artifact is pretty much a direct pull from that particular playbook. I wanted it to be something that was flexible, where the DM could decide what all fit into the umbrella of what it detects without having to tweak any actual rules or stats. The flavor text specifically calls out celestials and ancient artifacts, but it's easy to kitchen-sink it as anything that'll cause mental scarring. And since the sensitivity varies from amulet to amulet based on what the amulet has been exposed to, it's easy to finesse the usefulness of the specific amulet(s) your players end up with.
The inspection time was set somewhat cynically. You could easily use the familiarity/ambiguity dynamic in the flavor text to tune the action economy to your liking, but I wanted to set the baseline read-time to a minimum of one round. If there's a big or immediate threat, they won't need to inspect it (because it'll be shining bright enough that they won't be able to ignore it), but there'll still be plenty of scenarios where your players will *want* to look at it in the middle of combat. With a one-round baseline, it's long enough that they won't abuse it in combat, but it's also short enough that it shouldn't feel like a punishment. In theory.
May 18th: Template Update