The Magnum Opus is a customisable vehicle created by Chumbucket with the help of Max Rockatansky. Chumbucket led Max to the vehicle after Max's V8 Interceptor was stolen by Scabrous Scrotus. Chumbucket showed Max the plans for upgrading the Magnum Opus, as well as how he plans to replace the V6 engine with a V8. With Chumbucket's help, Max upgrades the Magnum Opus to be better than his stolen Interceptor. Along the way, Max helps out certain characters who help him progress in boosting the capabilities of the Magnum Opus in exchange for said help. Eventually with the help of Chumbucket, Max finds a V8 engine to fit the Magnum Opus so that it would be equal in terms with the Interceptor. After the Magnum Opus has been upgraded significantly, Max tracks down Scabrous and takes out his war party, this battle leaves Scabrous on the edge of a cliff awaiting one more push to send him and his vehicle off the cliff. Chumbucket realises this and clings onto the front of the car, attempting to persuade Max to leave the car as Max has decided he will do it with the Magnum Opus. Max furiously rams the Magnum Opus into Scabrous's vehicle to send it over as Max jumps out of the car. The Magnum Opus along with Chumbucket are destroyed in the collision, bringing an end to a car that rivalled the Interceptor.
The Magnum Opus is unique in the sense of being the only car that Chumbucket rides with Max and having unique weapons, such as the Harpoon, Thunderpoon and Sniper rifle.
The car has six potential bodies:
- Death Rattle
- Die Rolla
- Wild Hunt
- Ripper (DLC)