[quote=@Zyx]
<Snipped quote by souleaterfan320>

So you've no means of tracking or detecting them then? Surely they must leave [i]something[/i] traceable behind.
[/quote]

Temporal traces that lead nowhere. However they do it, they do it well. It's just best to try and catch them while they are around. 

*Flicks a crystal into the air, and catches it*

Or bust one of them wide open to take a piece, yourself.  No idea on how long the crystals stay active once separated from the body.