Dark Tales from Dreamdale by Jeremy Robertson

When a scary nightmare creature escapes its underworld prison, a brave boy, Arden Wonder, must slay the quirky dream monster Count Comatose before the villain has an opportunity to feed on the dreams and nightmares of young souls that will allow Count Comatose to unleash a nightmarish apocalypse that will corrupt reality. Every dreaming child will turn into fantasy creatures and be the monster's slaves in its lair--forever.