Rodimus Cron was created when Overlord jabbed Hot Rod in the chest with a shard of Unicron, corrupting him into a darker version of himself.
Power of the Primes
Searching for Megatron and the Requiem Blaster, Rodimus Cron and Overlord attacked the Combiners; killing Computron and severely injuring Devastator and Menasor. Overlord then demanded that the two remaining Combiners tell them Megatron's whereabouts. Undeterred, Menasor and Devastator stand up again and attack the two are easily repelled. Rodimus brings down Devastator down as Overlord holds Menasor in place. When Menasor refuses to reveal Megatron's location, Overlord orders Rodimus to destroy each of Devastator's limbs one by one. Eventually, Menasor cracks and reveals Megatron was headed for Primal Swamp, only for Rodimus to deliver the killing blow to Devastator anyway. His purpose having been served, Overlord crushes Menasor's neck and watches their sparks fly away before he and Rodimus depart for the swamp.
Upon their arrival, Rodimus and Overlord spotted the Dinobots and interrogated them for Megatron's next destination, to which the Dinobots claimed he was heading for a "library". Unicron then possessed Rodimus Cron and stated they were going to the Atheneum Sanctorum. The two picked up the trail and eventually reached the library, where Overlord attacked Megatron while Rodimus Cron fought Windlbade and Victorion. Killing Victorion, Rodimus Cron turned his attention to Windblade, who tried to compel Hot Rod to come out, but to no avail. Rodimus Cron was later temporarily taken out when Megatron fired the Requiem Blaster at Overlord.
He got up just in time for Megatronus Prime to arrive and snatch the Blaster before fleeing. Now fully possessed by Unicron, Rodimus Cron went after him.
Rodimus Cron later showed up at the battle between Megatron, Windblade and co. and Megatronus Prime. He reverted back to Hot Rod after Unicron left his body to try and possess Megatron again.