Obsidian and his consort Strika have fought 100 battles and succeeded in winning them all. Obsidian at first acted like a simple minded drone in his first appearance, only saying the word obliterate. He dropped the gimmick of saying obliterate once the trick was done.
Obsidian is a top strategist and views himself as a defender of Cybertron. His loyalties however, lie with whoever is in charge. He is not loyal to the leader so much as to Cybedrtron itself. Megatron activated his spark in order to use his strategy against the Maximal's. After ambushing several Maximals and forcing them to retreat into one location, Obsidian demanded surrender. ""Megatron IS Cybertron. To defend one is to defend the other. And to betray Megatron is to invite death." Botanica then arrives and frees the Maximals, but Obsidian had "revealed" the location of sparks to Optimus Primal. The plan failed and after Megatron was destroyed they pledged their loyalty to Optimus. Fellow Vehicon Thrust told him that if he was loyal to everyone, he was loyal to no one. Obsidian began to wonder about Thrust's words and when Megatron's spark possessed a diagnostic drone; Obsidian once again pledged loyalty to him. His final assault against the Maximals would end up with him being blasted into orbit.
It was originally intended for Obsidian and Strika to return to Cybertron after the reformating. They opted not to be turned into techno-organic beings as a form of punishment. This was idea was scrapped though.
In this universe Obsidian was an Autobot general who was forced into his Vehicon helicopter form to serve Megatron. Obsidian acted loyal to Megatron, but he secretly wished for revenge. With the help of Tankor he eventually overthrew Megatron and became tyrant of Cybertron. He and Tankor instilled fear into the inhabitants of Cybertron, this was until Unicron took Obsidian from this universe to serve his own purposes.
Unicron brought Obsidian(along with Tankor, Razorclaw, Reptilion, and Striker) to watch a deathbattle of different Transformers from alternate dimensions. Silverbolt, a contestant in the deathbattle, recognized Obsidian, the feeling was mutual for Obsidian. Obsidian had noted though that Silverbolt in their timeline had died screaming.
Eventually all the contestants were freed. Unicron disappeared underneath him and Nemesis Strika and they fell to their deaths.