Amulet of the Solanum

This carved bit of polished obsidian roughly the size of a dogtag hangs from a simple leather cord. As part of the process of attuning to this amulet, you may offer a drop of your blood to its center. When you do, the amulet permanently marks you with a magical aura only detectable by others that have been marked with the same aura. Spells like detect magic and other divination effects will fail to notice the aura, and it can be dispelled only by a casting of wish from a caster bearing the same aura.

Once marked, you gain the ability to perceive others similarly marked. If you can see them, they are outlined in a shimmering shadow noticeable even from a great distance. If they are within 120 ft. of you, you sense their presence, even if you cannot see them, though this sense is blocked by 1 foot of stone, 1 inch of common metal, a thin sheet of lead, or 3 feet of wood or dirt.

Once you have attuned to this amulet, its effects always work for you, even if you lose attunement or discard the amulet. Once the amulet has transferred its mark, it becomes a nonmagical item.