The script can be read here but below is a synopsis.
The heroes are in a desert fleeing from giant wasps after Eric accidentally bounced a rock off of their nest. Cornered, they fight the creatures but Presto wins the battle by conjuring an electric fan that blows the wasps away. Dungeon Master appears and Eric berates him for not stepping in sooner to help them and makes a casual comment about how if he was Dungeon Master things would be different. Dungeon Master accepts this as a challenge and zaps Eric so that he is also wearing the Garb of Power and can dispense the sorcery that comes with it. Dungeon Master than scolds Eric for conjuring a drinking fountain as there is what he describes as a universal balance where by conjuring water there may deprive farmland of water elsewhere and render it desert. He then tells the heroes to head east to find the Golden Grimoire that is inside the city of Darkhaven. Eric asks about his vanished shield but Dungeon Master explains that knowledge will be his shield. The heroes trek east while an eavesdropping shadow demon follows them.
The doubtful heroes quiz Eric about what he can do with these new powers and Eric realises that he can probably send them back home, and that this is what the Golden Grimoire must be for. Again, an eavesdropping shadow demon flies off to inform Venger.
In one of his castles Venger is pleased to hear from shadow demon that the heroes are seeking the Golden Grimoire as he can follow them to it and steal the book for himself.
On a cliff top Eric is attacked by a yeti that Hank binds with an energy arrow and the others mock him for not being able to use Dungeon Master's powers to save himself. Trekking off again, a nightmare-mounted Venger arrives with shadow demon and is amused to find Eric garbed as Dungeon Master. He then summons a storm to see whose sorcery is greater.
Eric spies the storm and deduces it is the work of Venger. The heroes flee as the storm follows, hurling lightning bolts at them and destroying a natural bridge. Hank fires an energy arrow to make a substitute bridge and the heroes cross the chasm. Eric then uses his sorcery to dispel the storm.
Venger comments to shadow demon that although Eric has much power he has little experience. They then depart to Darkhaven.
The heroes ponder a quicker way to reach Darkhaven so Presto attempts to conjure a flying carpet but instead produces a winged carpet that flies off without them on board. Eric then uses his new powers to summon a roc to ferry them there, however the roc is soon attacked by a fire-breathing red dragon.
The heroes elect to jump off the roc rather than face the battle, expecting Eric to save them, but as they tumble to the ground he is unable to muster his powers. Presto conjures a parachute from his hat instead and the heroes all grab on, except for Eric who loses his grip and has to be saved by Hank who fires eight energy arrows into the ground that bind together to form a trampoline for him to land on. Eric is despondent that his Dungeon Master powers failed and nearly killed his friends.
Crossing over a hill the heroes find Darkhaven and go to enter the enormous city but find a magical force field over the doorway. Bobby offers to smash it down but Eric says it won't work and uses his power to dissipate the force field instead.
A nightmare-mounted Venger and shadow demon smash their way into Darkhaven through a dome, urgent to find the Golden Grimoire before the heroes do.
Meanwhile the heroes are wandering through the city apparently lost, despite Eric claiming that he knows the way. A similarly lost Venger admits that it would take years to find the Golden Grimoire in such a huge city and decides to follow the heroes instead, confident that Dungeon Master's power will guide Eric to it.
The heroes come to a canal and catch a passing gondola. A giant octopus grabs the gondola but Eric uses his powers to make it release the boat before summoning a waterspout to elevate them up to where the Golden Grimoire is. Emerging through a hole in the floor they find the library that contains the magic book.
Leafing through the Golden Grimoire Eric recites a spell and opens up a portal home to the fairground, much to everybody's delight. Eric instructs them to leave their totems there along with Uni, who he claims would not survive on Earth, but adds that his magic will protect her.
The heroes are about to enter the portal when Venger blasts down the the door and fires a mystic bolt at the portal, causing it to shrink. He then snares the discarded totems as well as the Golden Grimoire. Eric urges the heroes to go through the closing portal while he battles Venger.
Not wanting to abandon Eric to the mercies of Venger Diana retrieves the discarded totems and hands them back to the heroes. Venger turns his anger on the armed heroes instead, but Eric distracts him by zapping Venger resumes his attack on the cavalier. Spying the discarded Golden Grimoire Eric remembers Dungeon Master's words about knowledge being his key and uses the book as a shield against one of Venger's mystic bolts.
The Golden Grimoire explodes with Venger cowering from it, while Darkhaven begins to collapse. The heroes find that the portal has shrunk to nothingness so Eric conjures them onto a nearby hill overlooking the doomed city.
Darkhaven explodes and Venger's gigantic spectre rises from the ruins and menaces them briefly before vanishing altogether. Eric is despondent that he failed to send his friends home and destroyed the Golden Grimoire but Dungeon Master appears and says it is a victory because he was willing to sacrifice himself battling Venger so that his friends could flee through the portal. Eric asks to be turned back into the cavalier and Dungeon Master complies but warns that once you have been touched with power you are never quite the same. Eric agrees, saying to his friends that he should get more respect because of it. With a cocky click of his fingers a downpour materialises above Eric and he ends up using his shield as an umbrella.