Adventurers needed to take a castle back from a Dragon

Party returned to the Warring Plane only to find it overrun by monsters with an evil Maiden and Ryan nowhere to be seen. In order to help track down the Maiden for a possible victory, Party was tasked with infiltrate a castle that was overseen by a dragon in order to steal plans on The Maiden's movements. They sucessfully used the new technology and Ol'McDonald's mech to dig underneath and managed to avoid detection while moving with an army of 10000. They snuck in within 4 rounds of combat and managed to defeat most of the forces, until the dragon decided to return. Where they successfully were able to run away.