Roger Pink-Eye created the Mold Monsters (by infesting cheese with black mold).
The Mold Monsters were created to reveal Ty's and Abby's secret. The are the second, third and fourth monsters created in the show. The first one was Frankenbooger.
Unlike real mold they can Move. They also has the ability to see. The can change their arms into an axe. Like real black mold they can make people sick.
The have two weaknesses. 1 light, the first Mold Monster was defeated with a lamp. The second one was killed with sunlight. The last Mold Monster was killed with bleach.