Atramentum's Indelible Mark

You point your finger and fire a tiny quantity of magical ink at a creature within range. The target must make a Constitution saving throw. On a failed save, you always know the target’s location until the spell is dispelled, but only while the two of you are on the same plane of existence. While you have this knowledge, the target can’t become hidden from you, and if it’s invisible, it gains no benefit from that condition against you.

If this spell is dispelled, you know immediately. The spell is automatically dispelled if the marked creature dies.

The maximum number of creatures you may have marked by this spell is equal to your spellcasting ability modifier. If you mark another beyond that, the earliest active mark is dispelled.