Corrupted Water Crystal
 
http://www.reignofangels.com/jewelry/pandora/fandom/final-fantasy/jewelry/corrupted-water-crystal/ 

Like a good many things, this started off as a nebulous concept I  hadn't taken in any way seriously until it was too late.  My girlfriend  had been talking about wanting some version of a water crystal pendant  (ala Final Fantasy 1), with the mention of "corrupted" in there  somewhere, and the Fiend responsible being the Kraken so tentacles were a  given and... I let my mind wander and tried a few things with a spare  crystal I'd had around for ages to add color and some extra sparkle.  I  was only encouraged further.

Several layers of sparkly and a wide variety of techniques later  and ta-da, there be a corrupted water crystal.  As is the standard case  with me, trying to get a decent representation of the colors under  various lighting proved... challenging.  There's a depth of purple  beneath the blue, and the crystal itself remains translucent, so  depending on how the light bounces and how much there actually is  shining on it, the crystal itself has waves of both purple and blue,  while the tentacles are always a darker blue with an opaque black base.