Major Story Arcs
For more information see : Batman: Reborn
When Mr. Toad is arrested Phosphorus Rex, Big Top, Siam and a group of Dollotrons, drive to the Gotham Police Station to break him out. Rex tricks the officers outside into thinking he is on fire and burns them when they get close. Rex then heads inside where he set others on fire. Batman soon shows up and during a fight sprays Rex in the face with a fire extinguisher. Later Batman takes Rex out of jail and drags him next to the Batcycle demanding Rex tell him who he works for. Rex finally breaks and gives the location of Professor Pyg.
A Court of Owls
For more information see : A Court of Owls
While Batman investigates Dan Matthews, a guard at Arkham Asylum who maybe on the take, Dan in a desperate attempt to get away, opens several of the inmates cells. Rex is one of those inmates seen attacking the Batman before the Joker appears to come to Batman's aide and the pair work together to beat back the group of rampaging inmates.
In other media
Phosphorus Rex appears in the animated series Beware the Batman. He secretly poses as Tobias Whale's lawyer, Milo Match, while actually serving as his fiery enforcer, Phosphorus Rex. He orders the kidnapping of Barbara Gordon in order to force Lieutenant James Gordon to free Whale. However, Batman and Katana arrive to free her and defeat Rex.