Castle Blackstone was a mysterious and seemingly abandoned old castle with spikes portruding from it's towers and walls. Somehow, Prime Evil was in possession of the keys to the castle.
When Count Freeze promised Prime Evil to lure the Ghostbusters into a trap and freeze them, he asked permission to use Blackstone to set his trap. Excited by the prospect of seeing the Ghostbusters defeated and out of his way, Prime Evil handed over the keys. Brat-A-Rat immediatly surmised that Freeze only wanted the keys so he could search for The Wizard of Blackstone but Prime Evil ensured him that there was no wizard at the castle.
Freeze managed to lure Eddie Spenser Jr. to the castle and capture him, and Eddie was soon followed by Jake Kong Jr., Tracy the Gorilla and Jessica Wray. After freezing them, Freeze also froze Brat-A-Rat, who was keeping an eye on him. Freeze did indeed intent to search for the Wizard of Blackstone, but Prime Evil himself arrived and quickly defeated Freeze using a fireball.
Only Eddie Spencer managed to escape from his ice cube prison and bumped into the long lost Wizard of Blackstone, who lived in a painting that was hanging in plain sight on one of the castle's walls. Taking refuge inside the Wizard's painting, Eddie was granted the wish to be turned into a smart and strong 'Hero of Blackstone'. The only catch was that Eddie couldn't tell anybody his true identity.
The Hero of Blackstone easily defeated Evil's ghosts and freed the Ghostbusters and Jessica. But Eddie soon decided that he would rather be himself than some unknown hero, and the Wizard gladly complied by taking away the powers of Blackstone once more.
Castle Blackstone makes it's only appearance in the episode The Way You Are.