Krool

"The main villain behind all of this is a character called Krool. He, or rather it, is an immeasurably powerful and malevolent force on the edge of existence that has watched with envy and waited with impatience from before the beginning of time, probing and testing the walls that keep it on the outside of the universe, trying to force its way in, just for an opportunity to spoil you day.  He intends to do this by creating a thing called entropy.  This will turn everything in the universe back into the energy that it's made from.  Krool will then take that energy and fill his face with it all until he's fit to burst.  But don't expect a huge invading army to come storming through from the Nth Dimension, Krool's far too sneaky and sly for that.  He's slow worming his way into out universe by taking away all of the fun.  If you don't have fun, then, you don't really feel like doing much and if you don't feel like doing much then entropy sets in and that's just what Krool wants; his mouth's watering at the thought.

If Krool had his way, we'd all be wearing sensible shoes instead of trainers, eating green veggies instead of burgers and no one would be playing computer games at all! But Krool realizes that total entropy must be accomplished in stages, and on your world the attacks have just begun." (1)

Krool is reputed to hold audience at the mythical Alter of Drear Reality. This is located at the Temple of Oblivion which inhabits many of Mental Block's creations. (2)

Throughout the book series Krool, a creature that lived in the void, would appear as non-physical pair of eyes in the physical realms. Towards the end of first book, Zool Rules, Krool used Zool's creative energy to enter the physical world allowing readers to see Krool's true form briefly. (3)

(1) "Zool Rules" Page 11-12 (2) "Zool Rules" page 36

(3) "Zool Rules" page 116-117.