The medallion will vibrate when within 100ft of any source of magic, or magical creature with a CR below 6. You do not learn the precise location of the source or creature, only that the medallion vibrates more intensely when closer to the source or creature.

No aberration, fey, fiend, monstrosity, or undead creature may consciously and willingly make physical contact with the medallion.

The medallion can be lost, stolen, or destroyed. If this happens, remove the medallion from your inventory, and lose the ability to detect magic and creatures this way until you replace it.