Crystal Mark

You create a visible or invisible magical mark on the object or creature within range that lasts until dispelled or discovered.  You can have up to 10 + your spell-casting modifier marks active simultaneously.  Many bounty hunters or thieves will make proper use of this spell.

The spell requires a Seekers Crystal or Enchanted Magical Stone in order to function properly.  If you lose a Seekers Crystal, you may create a new one using a potent magical gemstone and enchanting it with the Seekers Crystal ability with a successful ARCANA DC 20.  The Seekers Crystal functions as a compass - closing in on the distance of your marked target.  The Seekers Crystal will make a 'ping' sound once when you are 320ft in range of your target, twice when you are within 80ft in range of the target, and thrice when within 30ft of the target. The DM may require you to make a PER or SURVIVAL DC when searching for a marked character in a large crowd or a small object in a pile of golden treasures - even when you are in range of the spell.

The target has to make a successful PER 15 or ARCANA 15 to identify the mark.  If the mark is invisible, it cannot be identified by using PER.