"Bad Build" is the sixty-sixth episode of Dinotrux and the seventh and final episode of season seven, also known as Dinotrux Supercharged.
D-Structs traps Ty's group atop a rock pillar over a tar pit, but they manage to use on-hand supplies to build a collapsible ramp and make their escape. Frustrated, D-Structs returns to the Fortress of Fear only to be visited by D-Stroy, who was observing D-Struct's latest attempt to eliminate the Trux. D-Stroy offers to help D-Structs, and insists that his plan is one that can only work if the two of them cooperate. He then leads D-Structs and Skrap-It to his intended weapon: the Dreadtrux.
Using D-Structs' knowledge of combating the creature and a cache of helium Ore found by D-Stroy, the two train the Dreadtrux. Rather than having it attack directly, however, D-Structs proposes a plan that will cause Ty and his friends to contribute to their own defeat. They launch their own attack on the Flatirons, causing considerable damage to The Garage and various builds before retreating. During the rebuilding process, Xee-who has encountered D-Stroy previously-notices signs of his presence at various locations.
With Revvit's help, Xee determines that D-Stucts and D-Stroy have sabotaged the rebuild by planting helium Ore among the supplies used by the Trux. This lures in the Dreadtrux, which begins destroying the various builds to get at the Ore. Ty ends up locked in battle with D-Stroy, while the others are prevented from stopping the Dreadtrux by D-Structs. Unable to deal with this overpowering attack, Ty's group flees, with Revvit and Xee remaining with the Trux while the other tools head back to the Reptool Ravine.
Ty leads the group to the Bridge, only to find that D-Stroy and D-Structs have blocked it with helium Ore and are pursuing them along with the Dreadtrux. Xee leads the group into a ravine, and they manage to reach a secret entrance to a hidden forest by using the collapsible bridge built earlier. D-Structs and D-Stroy are puzzled, but D-Stroy is determined that the two of them will conquer the Crater and more. Having learned that D-Stroy is D-Structs' brother, Ty sets his plan to train in the secret forest until they're ready to take down the two T-Trux.