|HIT * 95%||Attack Element: Physical|
|Collapse Effect: Boss||State Resist: Fallen|
|State Resist: Scared||Stun * 50%|
|State Resist: Paralysis|
Rex Thunderstorm is the leader of the Gale Motorcycle Club in Area 3 who, shortly after kidnapping a party member, turned into a gruesome Joy Mutant with long arms, constantly holding his motorcycle over his head.
The gang's kidnapping is encountered during the camp in Area 3, where Lisa hallucinations are watching. Instead of the Blue Rockets or the Pretty Boys kidnapping them, the Motorcycle Club will leave the note, telling Brad to find them to rescue the party member.
At first glance, it would seem that this would be a standard Joy Mutant fight. However, Rex Thunderstorm possesses the Bike Slam attack. Bike Slam is an extremely powerful attack which will most likely KO whoever it hits, and even if they survive, they probably will be stunned. This is also his most frequently used attack. Rex may "trap" you into having one character constantly need to revive another, just to have another party member knocked out again. Along with this incredibly strong attack, there is still a decent chance that he will use Neck Break to permanently kill a party member as well. These two weapons place him among the most challenging foes in the game, so remember that this fight is optional.
- When attempting to get your kidnapped party member back the entire Gale Motorcycle Club will have been brutally killed by Rex. After defeating him Brad can examine a mound of dead meat on the edge of the cliff, which can be implied to be the remains of your kidnapped party member.
- Because of this series of events that occurs, it is impossible to rescue the party member that was kidnapped by the Motorcycle Club.
- Upon death, Rex will drop the Motorbike Helmet, a mask with an extremely high defense and one of the best pieces of armor in the game.
- Rex Thunderstorm is one of the only Joy Mutants who does not use Soft Skin as his battle theme, the only other being Hawk. Rex Thunderstorm's battle theme is instead Welcome to Hell.
- Rex Thunderstorm is one of the Joy Mutants seen prior to mutation. Others include Punkert, Blue, and technically Hawk.